Boyfriend trouble

So my boyfriend and I have been together for 7 months. Recently, he's been telling me he's going to ask me to marry him for Christmas (he's very serious too.) also, he told me that he wanted to have a baby soon and was trying to get me pregnant. I'm 18 and he's 17. This is my first serious relationship. Because he started saying this stuff, I got freaked out I guess and now I'm having doubts. Earlier I asked him if we could go on a break because I need to think things over. He flipped out on me and demanded that I get back with him. He thinks I'm trying have sex with other people. I have met up with an ex recently though when I stayed at my cousins house. We had a summer fling a couple years ago and all those memories came rushing back. I'm not really sure what to do. Just so confused.