Escape from the side mount or side control.
This is a very common position in Brazilian jiu jitsu and professional fighting in general. I never have my limbs hanging out like so, because then he can trap it and attack it, OK, and put you in a lock. So, any time you're at the bottom, instead of freaking out always keep your hands tight. It's very important.
I place my hands, first one under his throat like so, my other hand is at his hip. Notice that the elbow is tucked under him. If it's out, it's wrong. He's going to drive his knee higher, and he's going to have you much more trapped.
So, I'm going to have my hand at the hip. My elbow's tucked under his body. At this point now I'm going to bridge and hip escape. I will never try and bench press him off. It'll never work, OK. Even if you're bigger than him, this, look, this is not going to help you. All in your hips. Bridge up. Notice that my heels are off the ground. It gives you the maximum bridge. Now I'm going to hip escape. Pushing off my feet I hip escape.
My leg now is going to come through. This leg specifically, the bottom leg, becomes a barrier between us. He tries to advance here. Look. I just stretch it against him, come all the way around, and have him in closed guard. If I have to be at the bottom I prefer that my opponent is in my closed guard where I have more control of him.