How do i leave

I've been in an insane toxic relationship for years. I got out last year, because I finally had enough but I still talked to my ex. I cut ties with him completely in March, all the way up to last week. That was the longest I've gone without talking to him. I felt the need to text him because I was so alone, felt like I had nobody to talk to and like I needed to hear what he has to say. Especially because of lockdown here, i feel super lonely. I caved in and texted him. He was an asshole of a boyfriend to me, manipulated me and many more things. I just want to leave but it's so hard. I wanna be okay and I wanna find other guys attractive and be with them. But my ex never made an effort to ever see me or do anything so I was in a relationship of 3 years with no experience with guys. Im scared if I don't leave this toxic cycle I won't be able to pursue anything with anyone else, he's already taken all my high school years of experience with guys away from me and now that I'm 19 he's taken away my first year of university. I don't know what to do