My boyfriends mood swings are absolutely tearing me up inside.

One day he's talking about what our kids names will be and where we should get married, and the next day it's like he's completely pissed off and talks to me like I'm annoying that ever living shit out of him. I've asked him a couple of times if I'm annoying him and he gives answers like "no?" And then goes back to being annoyed. Then sure enough the next day telling me how much he loves me, and wants to cuddle all day.The thing is, I absolutely love the guy. In every way he is my absolute dream. Just thinking about him gives me butterflies in my stomach. But this seems to be a recurring thing with him, and almost seems to be getting worse.It's killing me inside. I'm worried I'm annoying him and he won't tell me, I'm worried that I'm not doing enough to cheer him up, or I'm worried that he's becoming really depressed.Like I said above, it's tearing me up it's the going back and forth over and over of worrying and butterflies.What do you guys think of this and how I should handle it?