My boyfriend is married.. :( Should i break up with him? help!!!!?

Ok, my boyfriend is married, but he is going to get a divorce soon. Not because of me, but because his wife had a baby by another man and has being cheating on him all along. I feel that he thinks that i am like her, that i am going to be cheating on him also. I am 18 and he is 35. I love him, but i question his love for me sometimes. He thinks that i am soo smart and that if i cheat on him he will never know because i am smart and would come up with a good excuse. He doesn't trust me and that makes me feel like i can not trust him. He has 6 kids, and keeps taking care of them after he found out the she cheated on him and honestly i don't think anyone of them are his. by luck maybe one because she even cheated with a 70 year old. I don't know if i should ump him or not. I dont think i could leave with a man who is taking care of other men's babies and is not willing to help me with anything i need. what about my BABY. i feel bad for him in one way but i am sooo mad also. How could he not see that those kids are not his. How could someone cheat on you for 10 years and you not question the children. I am SICK OF IT! i need advise on what to do about this situation, please help me.