Emotional boyfriend... why do I find it odd?

So my boyfriend and I have been together for about 5 months and I've seen him cry 3 times over different things. I've only cried once during our relationship and I was drunk. The first time he cried was because I was in horrible pain because of a uti and he thought it was his fault that I had it. The second time was because he just started thinking about his life and the stuff he has been through. Then today he cried because we were watching a movie and the girl was talking about how when teens who were sheltered get older they rebel and go hard core. Well I made a comment and was like I should show my dad this movie and the girl had just said something about fucking a lot of guys but I didn't think of that. So he said words hurt you know and then as a joke I said didn't your mom or anyone ever teach you "sticks and stones may break my bones but words will never hurt me" and then he was like my mom never taught me shit (she wasn't really in his life) and no one else taught me anything, I taught myself and took care of myself. And he got upset and cried. I didn't mean to offend him. I felt terrible! But how do I comfort him? I'm not use to being with someone who is emotional. I understand why he is but idk how to comfort him and I want to so he knows I'm here for him.