I've never been in a close friendship like that where I might fall in love, but I know how it feels when a valued friend loses interest in me after becoming infatuated with somebody.

I would simply pretend that you are busy with other things and drifting away from your friend (rather than the truth that you feel hurt by his attraction to somebody else). He hasn't done anything wrong - in fact it sounds like he cares about you as a friend. Otherwise, he would simply spend all his time with his girlfriend and never see you at all.

I can certainly understand why you don't want to spend time with him now, because it is a reminder of losing a close friendship. The love you feel for him is a different dimension where I have no experience. Hopefully my ramblings give you some help of some kind.