Anxiety or wrong relationship

Hi, please please help.
I've had this issue since I started dating at 17..in short never managed to have a successful happy relationship, a few months into the relationship I freak out, question my feelings or apparent lack of and bail. Usually putting it down to the fact that it must mean they are the wrong person for me, I fret with anxiety so to relieve it I'd leave. I tootle on with my life get 'better' again then the process repeats. every romantic relationship since, I've been the same, always battled with my thoughts then bailed. I've also battled with my sexuality, ie does it never work cause I'm lesbian? When I was 18 I fell really hard for a girl, the first girl, and I've never stopped thinking about her. I never felt this way about anyone since. I've dated girls here n there over the years but not managed to have an actual relationship with a woman. I've dated men and women, class myself as bi, I'm 31 now, the only serious (long term) relationship I have ever had was two years ago, lasted three years and he was incredibly abusive in every way. He sexually emotionally and mentally abused me. So that didn't help. Now I've met an incredible man who when I'm "normal" (I use that term to describe me when I'm not a raving loon with anxiety) seems perfect for me. I really didn't expect this freak out to happen again and I'm just too tired of it. Surely it's me and not him cause you can see the repeated history, but yet I can't seem to shake off that it'd all be easier on my own, even though the inevitable will happen and I'll end up being miserable on my own, I don't understand why I feel one way one minute then like I never really loved him at all is that possible? . I can't seem to get passed it, I feel trapped even though he is the most supportive and loving man, he let's me be me and have my space... Sorry if I'm missing out a few points here and there but basically I cannot determine if I'm just an idiot who does not know real love and thus gets anxiety when the relationship gets more serious, am I afraid if commitment, why, how do you get over this? I feel like my only option is to bail cause I feel like I have no feelings for him whatsoever, then I briefly feel again, but then fall back into the anxiety and feel sick at the thought of intimacy...which I tend to feel about two months into a relationship, since my very first at 17, which was a normal nice first love no drama or trauma... What the hell is wrong with me? I sound like a horrible person. All I want is to be happy and share that with someone, where do you know if it's the wrong relationship or the anxiety issues? Did you overcome it?
If I sit and think when I date a woman it's far more exciting... Am I just in denial? Or is my stupid brain making excuses or reasons to get out of a decent relationship with a wonderful man cause I'm a horrible person?

The thought of breaking it off makes me feel like sh** but I'm so used to shutting it out as I've had to since being a kid, parents divorced at 4, never firmed proper attachment probably... Again sorry for the jumbled post but I would be eternally grateful for your help x