when i'm rolling against stronger opponents and i can't pull guard in that situation, i've had reasonable success going for armbar/pressing armbar combos from there. so assuming your opponent has you in side control with his knees on your right side: you have your right knee in against his stomach, but you're having trouble getting him in guard. control his right arm against your chest, use your left forearm to bridge against his neck so you can swing your left leg over his head to go for the armbar. if it seems like you're not gonna be able to hold the submission, pin his left wrist between the right side of your neck and your right shoulder, let him pull out his right arm, continue to control his upper body with your left leg, and just use your arms to press down on his his left elbow from there.
i hope you know which moves i'm talking about, because that's probably not the greatest description. i dont know what your experience level is, so i don't know how much detail i should go into.