Question -- are you open to the idea of seeing anyone else? I'm not saying you should see someone just to "make up" for what you're not getting from your gf, but I think that just being open to the idea, flirting a little, might help you feel a little calmer. A couple months into my gf's pregnancy I made the conscious decision to be open to other things that might come along, to give me something else to focus on so that I didn't obsess endlessly over her. I ended up meeting a fun new lover and that did really help me be more patient with her.
I feel pretty strongly that if your only relationship is secondary, you should stay open to other loves, serious or casual. Otherwise you can begin to feel like "What's wrong with me that other people get a whole pie of love/romance/time/commitment/sex/whatever and I just get a little slice?"