We married last year, and like Feeb we invited anyone who was in a long term relationship. There were a couple of cases of new partners that we had never met (and in some cases did not know about until informed) and therefore they did not get an invite.

I think it is strange to not invite your partner - you have a child together, so you are obviously committed. I think you could still go but it is entirely up to you.

Weddings are so hard in this instance - but it is not like he is a boyfriend of 3 months that they don't know about.