My DP is expecting our first baby. She got pregnant partly because I have a history of miscarriage, which is being investigated at the moment. So far there's no definite indications of why it happens, but some tests have come up positive and so they're continuing to check things out.
Obviously, we're thrilled about the baby and I honestly don't feel the tiniest bit that she isn't mine. In fact we both regularly forget she won't inherit anything genetic from me. 
However, I feel a bit odd about the mental 'boxes' people put me in. We just did NCT, and we had a lovely teacher who was falling over herself to be inclusive, and everyone else there was really nice and friendly. Now we've finished the classes we were encouraged to set up little facebook groups - a general one, one for dads and one for mums. Perhaps predictably, the general one is silent, there's one for mums which DP tells me is full of chatter, and as far as I know, there isn't one for dads at all because no one's set it up. Or, of course, they have and I just don't know. I could set it up myself, but I'm a bit nervous, firstly because I know someone in the same situation as me who had men complain they couldn't talk freely in front of her, and partly because ... and this is bad ... I just don't feel as if I have so much in common with the men. Rationally, I know we share a lot of common ground, and they're all nice, but I feel out of place. And obviously I don't fit with the mums either. And I feel oddly lonely.
I am not generally one for language policing and so my issue isn't that I mind people talking about 'the dads' and including me, or referring to me as 'honorary dad'. I can't quite put my finger on it, but I just don't feel as if I have the same experiences as them.
I am sure this will all fly out of my mind once the baby's born and I'll be far too busy and sleepless to think about anything so trivial. But can anyone sort of understand why I'm feeling out of place, and help me figure it out?