really doesn’t know what to do ..

I’ve been talking to a guy for at least 9 months & everything was sooo good until In March I found out that he was in a whole relationship the whole time. now that shit broke my heart, like really broke my heart. we stopped talking for a couple of days but we eventually started seeing each other again. now for one I’m not one to interfere in ANYONES relationship, I felt as if you shouldn’t deal with anyone who’s in a relationship already. basically don’t wreck anyone home. I feel like a hypocrite & that I contradict myself because I should’ve followed my own gahdamn advice! he says he’s gonna leave her but I tell him that I’m skeptical about it .. now he doesn’t want me to leave but I have bad anxiety & I tend to overthink things but he tells me to think positive. like how tf can I stay positive in a situation like this? I really really do like him & I do wanna be with him because we’ve been through a lot honestly & I can see myself with him in the future but I’m just scared. Should I just leave? & just see what happens in the future? Please y’all be honest, if y’all been in this situation please tell me what y’all did.