Is it time to throw in the towel?

My partner and I have been together for nearly 9 years have lived together for 7 and in our brought home for 5.5years. He has 3 children from previous relationships (24 male, 14 male, 10 female) the younger 2 spent half the week with us each week and the moment they arrive he changes (but doesn’t see it) our 2 year old son and myself are totally sideline, I feel like I’m just there to was and clean after them. And my little one is constantly moaned at and told off. The behaviour from the 14 YO is aggressive and rude all the time (he dictates the roost at his mums) it feels like it’s getting worse all over OH is almost never home with me and the youngest in favour of the other two, Christmas Day he goes to his ex wife’s to see them for the morning birthdays etc. I fund everything for the 2 YO, clothes, food, nursery and days out. Does anyone have any advice? I’m feeling so low