It's gonna happen eventually. No matter how hard you work, how much effort you put in, at some point you're going to hit a plateau. Might happen in a month, might take you years if you're lucky and diligent with your periodization but it's okay. It happens to the best of us.
Controlled chaos. Induced damage. The entire point of working out is to traumatize your body a little bit. You are deliberately challenging yourself and your physiological systems in the attempt to make them better. The somewhat unfortunate other side of the coin is that means the better you get at something or the easier it becomes, the less it's doing for you.
It's easy to fall into a routine of doing the same thing if you're not careful. Even if you think you're doing all the right things, if you still aren't seeing the progress you're looking for it might be time to change something up a little bit. It doesn't have to be anything gigantic. I'm not telling you to completely re-imagine your entire fitness plan. I just want you to consider tossing in some of the following tweaks or paying attention to certain details. Just give it a shot. You might surprise yourself.
Ideas For Breaking a Plateau
1) Do Sets for Time Rather Than Repetitions
Stop counting reps and instead grab a timer and go for as many as you can in a certain time interval. You may have to lighten the weight a little but don't get carried away. The point is to push yourself. Do 3 sets of 30 seconds on the bench rather than 3 sets of 12 or try 5 sets of 20 seconds of as many pushups as you can. It's harder than you probably think.
If you're looking for a serious change try Tabata intervals. The basic idea is that you do 20 seconds of all out effort and 10 seconds of rest for 8 sets (3:50 seconds total). It works best with multi-joint compound exercises. Think bench presses and squats rather than bicep curls and lat raises.
Here's a nasty workout you can do with just a Pull-up bar and a jump rope.
Sample bodyweight Tabata workout:
Dynamic Warm-Up 10-15min
1:00 Jump Rope
Tabata Pull-up (you can substitute in jumping pull ups or an inverted row if the pull ups are too much)
2:00 Jump Rope
Tabata Sit Up
1:00 Jump Rope
Tabata Push Up
2:00 Jump rope
1:00 Jump Rope
Tabata Jump Rope
2) Start Using a Training Log
I'm a huge proponent of data collection. The best way to see what you need to change is having an exact record of everything you've done. It can be tedious at times but if your goal is to try to get stronger you need to make sure you're consistently increasing how much weight you're lifting. If your aim is cardiovascular endurance, you need to make sure you're always either pushing your pace or your volume a bit. It's hard to make sure you're consistently moving forward if you don't have a map of where you've been.
3) Change Your Diet
Even if your goal is not weight loss you may need to pay more attention to your nutrient intake than you think. One of the largest determinants of a positive hormonal environment is what you eat. Without getting into the details too much, the more processed something is, the more likely it is to cause a blood sugar spike which puts your body into storage mode and blunts the response of all those wonderful anabolic hormones. On the flip side, the closer you are to eating clean the easier it is for your bodies to keep all that good stuff coursing through your veins and making you stronger.
You also need to make sure you're fueling yourself properly. It's great that you started doing 2 a days and I respect your drive but you need to recognize that burning another 500-1000 every day requires a serious increase in food intake especially if you're looking to build any kind of muscle.
The average persons idea of what constitutes a large amount of protein is pretty far off from what you probably need. If you're very active (workout intensely 4-5 days a week on top of other daily activities) you should shoot for around 1g of protein per lb of body weight. It sounds like a lot, but if you're taking in a solid source of protein each meal and eating 4-5 times a day (which you should be) it's not terribly hard to hit.
4) Take More Time Off
Rest goes a long way. When I talk to people who can't remember the last day they took off it makes me cringe a little bit. You need to give your body a break sometimes. It's not just to increase your gains, although it can have that effect. It's to keep yourself injury free. If you are active you are going to subject your body to wear and tear. This is normal and healthy. Your body has all sorts of wonderful mechanisms for remaking you better, faster and stronger. The problem is when you never give yourself ample recovery time you are constantly in a cycle of breakdown. You're constantly catabolic. This can lead to inflammation and injury which will only further slow your gains. Wouldn't you rather voluntarily take a day or two off a week than a forced 6 months off for joint surgery and rehab? Because it can take that long. Hopefully you'll just have a minor overuse injury and some good ol' rest and ice will take care of it. Worst case scenario you're so overworked that you compromise your form and do some real damage, the kind that needs surgical repair. That can take anywhere from 3-6 months and if it's your shoulder or your hip there's a good chance you'll never be the same again. These kinds of injuries are more common in actual sports than the gym but the lesson is still the same. Don't be stupid. Get your rest.
These recommendations are mostly for someone who is at least moderately experienced and already has their bases covered. You should be doing some strength training and some type of conditioning along with some exercises for flexibility and mobility. If you're not doing all of this stuff, adding it in could be enough to get you through your plateau all in itself. If all you do is cardio, try a basic strength training program. You'll probably be blown away by the changes you'll see with just 2-3 days a week of total body strength work.
Always try new things. Always keep moving forward. One of the foundational principles of real fitness is the ability to tackle any physical challenge. The best way to stay functionally fit is to keep trying new things, whether it's a attempting a muscle up, dedicating yourself to power lifting for 6 months, or signing up for an ultimate frisbee league. Keep it fresh. Your body and your joints will thank you.
Dynamic Warm Up
Jump Rope - 5 min
Single Leg RDL 10x ea
Alternating toe touches 10xea
Leg Swings 10x ea a/p/m/l ea leg
Single Leg Bridges 10x ea.
Bird Dogs 10x ea
Push Up 10x
Jump Rope - 2 min
Power Clean 5 (95) 3(115) 1(135) 1(155) (warm-up) 5x5 at 145
Front Squat 5x5 205
Standing Overhead Press 3x5 115