Step child

We recently moved in with my in laws and my husbands baby is having a bd party. The previous year I didn’t care I guess bc I had my mind on other things. But this time I feel so left out, everyone makes plans around me and it just feels so ugly. I don’t even know what to do to not be home the night that they’re having the party. I feel so guilty for feeling like this. Does anyone else feel the same or it’s just my hormones taking over?

I got together with my husband when the baby was 1 year old. The mom has always been in a really unstable situation. I find my self having to help her out with money really often without her knowing it’s from me otherwise she won’t take it. My mother in law always pretends it’s her helping her out. Being involved is not really the issue because I put money for the party. This is happening at her house so I’m not welcomed there, she’s never been okay with him being with me and she’s always doing immature things. She has made scenes in public before, but I do it for my baby to have a nice day 😭😭😭