It's early, but because of the holidays I wouldn't make a big stink about that. As for your hubby's friends being invited - they are adults and can choose whether or not they know or care enough to attend or buy a gift - not for you to worry.
Now, as for you, I'm sorry you're having a difficult time conceiving. If it hurts too much to go, just send a nice card or gift (closer to the due date, if you prefer) and don't worry about the shower. The only think you can control in this situation is your reaction. If you are bitter, you are only making yourself miserable, not them. So, find something, anything, to be happy about and focus on that.
I hope you conceive soon and have a wonderful baby; but not due too soon after major holidays.