I had a similar experience about one year ago, I had rent a room in a house and fell desperately in love with a flatmate. I had the same symptoms you describe, and a couple of times I thought I might be close to having a heart attack just because she had walked into the same room. Quite stupid.
A strange thing that happened is that I felt the most ardent desire of her company when she was not there, and often in the middle of the night I would entertain the (very unwise) idea of rushing to her room and declare my love like in the 19th century. But then when I actualy was with her for a while, once the initial impact on my pulse and blood pressure had passed, I would become less interested.
Oh and no, I never managed to tell her, until I left
Horrible experience, really. But it shouldn't be so hard for a girl as it was for me. I mean I had no chance whatsoever, even though she did not completely dislike my company it was perfectly clear that she was not attracted to me in a romantic way. But you, as a girl, have many more chances of succeding. Besides, we guys are much more sensitive and polite (yes we are
) so even if he says no he will most likely say it in a nice, understanding manner. Just go for it, and don't worry.