I keep almost fainting!!

I am by no means a squeamish person, but only recently (I'm 34 weeks with first baby) have I begun to feel faint and lose my vision when thinking about labour and birth! Even taking the tour of the hospital made me get cold sweats, lose my vision and almost pass out! I know it's probably just nerves, but has anybody else had this problem? I know for certain when the time comes for delivery that I'm going to have these symptoms! Its the most unpleasant feeling and I really don't want to faint during birth or the next time somebody talks to me about labour!