nona • Young adult trying to find my way in this cruel world

My partner has three children from previous relationships, one of the children visits every 4-5 days for a certain amount of days, he works sometimes, so of course I help him as much as I can even when he doesn’t work. However, my partner wants me to be more involved as a second or bonus mom, the child’s ACTUAL mother who is very present and active in her baby’s life has already told me I would never take her spot as mom lol. Which btw I have never intended or tried to do. I mean hell I wouldn’t want my kids calling someone else mom if I’m being honest. My partner and I have these tiny arguments about it, and I just don’t know what the big deal is. Should I be stepping up more than what I’m doing? I mean I change her, I feed her, we play, I teach her. I just don’t want the mom title and I’ve explained this. She’s far too young to be brainwashed anyways. Besides, whenever a blow out happens they both do this thing where they tell me “they don’t want me around their baby” and then as soon as things are said and done they want me as her babysitter and “step mom”. Recently, the mother of the child told me she would grant my partner full custody and dismissed me and told me she didn’t trust me and didn’t want me around her child? But we live in the same home… whatever anywaysssss… lately, I’ve decided to step back and fall back and I guess I’ve been helping out less and interacting with the baby less than like I usually would and my partner feels funny about it but it’s like I’m damned if I do and damned if I don’t. I over step my boundaries with this child but I’m also not doing enough? Lol.

I don’t know sometimes it feels like I’m being used by them both as their occasional babysitter or care taker. I’m not sure if it’s a manipulation tactic or what, so that I can beg to see a child that isn’t even mine. I mean she is great and all and a fun baby, but I most certainly will not ever beg to be in a child’s life that I have no rights to anyway lol. Jsut so they can pull her away when they feel like it because they know that they can. It’s frustrating. Should I stop caring or keep trying?