Need some advice.

How many lies are you supposed to forgive? I’ve been with this guy for a year and a half we have 2 kids together. ( this isn’t the first time we have been together) he lives with me and my family. He lies to me constantly about everything and I’ve forgiven him so many times. I’m younger than I’d like to admit and my parents are in there 70s. Before things got bad me and him were talking about marriage. Now it feels more like I don’t have a choice in it. The only way my parents can make it is if I do marry him. I’m trying and trying but it hurts. He made me cut out pretty much everyone in my life and the only person I talk to feels like I need to start compromising with him even tho I try and try.