I can't say anything

My boyfriend and I have been togeher for a year and 3 months. I found out that he cheated on me in the first 2 months we were together. (With the daughter of the 34 year old he had dated for over a year at age 15). Now, he talks to the past 34 year old constantly and she tells him that she cant be happy without him. Well we recently found out that I am pregnant. 8 weeks. At age 16, my boyfriend is now 18. He doesnt understand why I get upset over them talking so much. When i try to talk to him about how i feel he just gets all pissy and doesnt want to listen to me. He has told me that he can only talk to 2 people about anything and everything...his best friend Zak and this 37 year old. I am not one of them. I asked him why he cant talk to me about everything and all he said was because I get pissy over everything he says. Well when it involves not treating me like his one of a kind girlfriend of course i do. when it involves threatening my family...of course i do!!! he just doesnt understand!!!!!! what can i do to make this right?!?!