Don't know how to leave

Hi! So I'm in a relationship with an older man he is 26 and I'm 19 we live together, we share one car that is technically his and I'm currently looking for another job . I no longer want to be in this relationship because I'm tired of the lies and coming second to his baby mama . I'm only 19! And I gave up everything my apt, friends anything that screamed fun and independent I let go which I shouldn't have done because he doesn't appreciate anything I do I understand I don't help RN with bills and stuff (his brother also lives there and his girlfriend might as well to as much as she's there, but he splits the bills with him) but I do watch his 2 kids 3 and 7 which is hard asf when they are almost half my age, I clean up after EVERYONE and cook for him and the kids. I'm just putting in way to much effort when he isn't doing the same, he's to busy showing love to his baby mama. This relationship has done nothing but ruin my self esteem and make my depression worst we've only been together 6 months and I don't want this to continue, I really need advice on the best way to get out of this situation before it ruins the woman I want to become