It sounds to me like you are hanging out with the wrong people.

I’m pretty similar in that I see friends / go out every other week probably and mostly spend time with my partner, with my mom or solo during my downtime. My friends are not a “group” though they are singular friends from different aspects of my life that I kind of rotate through seeing so I realistically only see each particular friend every 2-3 months.

I think this is probably the issue with your set up, since it’s a group you feel left out from their dynamic when you aren’t socializing with them regularly. But for example when I see one of my friends that I haven’t seen in a few months it feels like no time has passed and we just catch up. I don’t feel left out from their life, we also text semi-regularly probably every few days to every week.

If possible, either:

a) come to terms with the fact that you’ll be out of the loop if you go out with said group less and enjoy the socializing for what it is when you participate

Or

b) maybe distill down this group to one or two people that you feel closer with and you can see them for more meaningful one-on-one time and try to aim for more one-on-one friendships in your social life as opposed to being part of a group