This is a VERY dangerous situation!!! If he is already having erections in session 2 and grabbing you forcibly in session 3, there is a real chance he could rape you in the coming sessions. Are you willing to take that risk?

Since everyone has already told you he is unethical and he is not actually practicing therapy, what is the pull that is causing you to go back? Maybe if you explain why you want to continue with him-- despite the boundary violations-- we can help better give you the kind of feedback you're looking for?