Hi CupcakeJ, Welcome to this site.
I hope you can see this man for who he really is. He is a smooth talking cheater. You have no future with him. You feel good when your with him now but that will change. He is married with 3 kids, he will not leave his wife. (he probably doesn't want to) He is using you, just for a sexual relationship. Get out now, your stronger than you think. You can deal with your health issues alone. You will come out of this better without him. You deserve better. Good luck to you.