I’m assuming that you and your boyfriend have discussed the likely possibility of becoming engaged, so I’ll put in my two cents accordingly.
Guys act weird when they are gearing up to propose. In fact, I had a lunchtime discussion about this with several female coworkers just yesterday (they’re all getting married this year, and I’ve been married for almost two years now). All of us had very similar stories about the weird behavior from our guys. In fact, I was convinced that my then-boyfriend (now husband) was going to break up with me, because he was acting very distant, avoiding me, and telling me he “needed space”. Actually, he was trying to buy the ring without me finding out, and trying to figure out how to ask me. I’m not sure what I would have done if he had dragged it out any longer.
I think guys get freaked out about all the pressure, even if it’s something they really want. It’s a life-changing decision- if all goes as planned, their lives won’t be about just them any more. Plus there’s all the other stuff: is the ring too small? too big? is it too soon in the relationship? will her parents (or mine) be mad? can I afford this? am I enough of an adult? how should I ask her? what if she says no? what if she says yes? Lots of pressure on the poor guys. I’m sure the male half of these boards can weigh in further on this topic.