Thanks for the thoughtful reply, EugenePoet. That's a very good point about trying to become friends with my GF's lover, it might relieve some tension and anxiety I have about the whole affair (no pun intended).
As to the counselor situation I am faced with the need to find a new one since my current counselor works for the university I've just graduated from. My counseling experience has been very positive so far, though, so that's encouraging. Honestly sometimes I think everybody should see a counselor, it's so comforting to have somebody listen to your problems and offer non-judgemental advice.
Just surfing this forum and reading some people's stories has made me feel much better and more solid about this whole thing. It's a process, I can't expect to wake up tomorrow and undo a lifetime's worth of social programming for monogamy. One step at a time.