Should I leave him?

So my partner has this weird obsession with talking/ flirting with women online and going on dating sites.

We’ve been together for 3yrs and the first year was fine, we were happy and I never caught him talking to another women, but every since I got pregnant with our son, he’s just been talking to women every chance he gets but when I catch him, he promises me he’ll never do it again and he’s done and he wants me to trust him but then maybe 3 months later he does the same thing again, I find out, he promises he’ll never do it again and then again 3-4months later he just does it again, and this happens literally every few months like a relapse. I don’t know what to do, I feel lost and hopeless, I want to leave him but I love him and we have a son together but I don’t want him to keep doing the same thing to me, it’s like he doesn’t learn. I did threaten to leave but somehow I just end up forgiving him, like nothing ever happened. I feel like he’s taking advantage of me because he thinks I won’t ever leave him. I need some advice! should I leave him for good? And if so How do I get over him? I’m at a lost at this point 😟

(I’m 20 and he’s 22)