I allow a toxic person abuse me what's wrong with me

It's a long story but I want to share it. I was in an abusive relationship with the father of my kids. I had nowhere to go and didn't have any friends. I started chatting to a male online and it turned to sexual chat and this went on for 2 years until we eventually met. We met about 4 times then suddenly he messaged me and said I was dumped. I was distraught and begged and pleaded to reconsider as I began having feelings for him. I slumped into even deeper depression due to the abuse I was getting off my partner. The male I had a fling with would sent random texts with 'sex' or 'call me' and when I replied or called he'd get other women to verbally abuse me on the phone. He done it to me a few times until I changed my number. I split up with the kids father and after a while tried Internet dating. At first it was OK I was getting better but ex fling had other ideas and would send me messages though the online dating sites, at first I'd respond then I'd block him. This went on for a while. Everything went quiet until 2 years ago I received an email from ex fling  I automatically deleted it. Everything is fine again. I'm happy at work and life getting back together. That was until last week I noticed an email I didn't recognise the email was just 'hi' so I replied hi back. It was the ex fling, so I told him to go away but he insisted we have a chat. We met up and it resulted in sex and he couldn't wait to get rid of me. He sent a text later asking if it was OK when I said it was fine, he made belittling comments and laughing. I asked if we would meet in a hotel and he just gave 1 word replies. he has went silent on me again. I knew it was a bad idea to meet him, I have had  nightmares again  and not eating much and I've withdrawn into myself feeling like a fool. I start back at work next week and I can't face going. 

I think he has issues with me because this contacting me has went on along time over 10 years, I stopped responding 5 years ago until last week and know he will never stop doing this to me. And it's like I'm addicted to the abuse I receive from him. 

 I'm dying inside from shame of it all.