Feeling like I'm losing my friends to my partner

I can't help but feeling like I am losing my friends to my partner. I know that it's not a fair thing to think, but I'm not sure how to cope with these feelings. Both my partner and I moved to a new city about 3 years ago, with covid going on it had been a bit hard to make friends. They met some friends at language classes etc that they would sometimes hang out with. For me it's always been harder to make friends, so at my hobbies I haven't really met many people I connected with. Over these years, I did meet two people I connected with, at work (ex-colleague) and at a organized meetup during covid. And since these people were fun, and they also had partners who are from abroad (just like mine), I had proposed at some point to meet with the partners, so they also get to meet people who are new in the country etc. So we've been meeting in group mostly since then. Now we're all super busy and tired a lot so we meet like once a month tops I would say generally. We haven't become super close friends yet, but we were kinda getting there. But now, this one friend and my partner decided to go running together once a week; and the other friend and my partner have decided to go to the gym together once a week. Which means that my partner gets to see their own friends + "my" friends (which had become our friends) every week, which is possible for them because they have very flexible schedules and they just meet during the day. It was hard to meet my/our friends already, now if they see my partner every week I feel like I will never see them anymore, and when I see them they'll have nothing to share anymore, and that they will just become my partner's friends. My partner is also a very charming and social person, and people generally always like them - while I am more shy so people may not feel close to me immediately. And even while we were meeting in group these past months, I've always felt so insecure that they are starting to like my partner better than me. I know I may be overreacting, they're meeting for a specific reason, and even so - everyone is free to meet with whoever they want of course, but it's just really not so easy for me to find friendships so it feels super discouraging to me. And on top of that, I had been wanting to go to the gym too, so I have told them that maybe I would like to join and they are both fine with it. But my friend and partner have agreed on a moment already that suits them both, that is during the day and so hard for me to make it. I can rearrange work to join, but I just feel like I'm crashing the party and if they haven't asked me for my availability even if they know I wanna join, and I can just join at whatever moment they decide, it doesn't really feel like I should. Just makes me feel very sad and I feel like I have to start all over again to find new friends. Any advice on how to deal with these feelings?