Anxiety after abusive relationship

[Butningembers]

I've seen a few similar posts on here but felt the need to post myself
Recently I've started to struggle from anxiety and I feel it all stems back from an emotionally abusive relationship I had around 7 years ago
We weren't together all that long (around 1.5 years) but we had been quite good friends for a number of years prior. When we started the relationship I was extremely confident, outgoing and generally a really fun person to be around. To cut a long story short, when the relationship ended I just assumed I was the same person and it's took quite a number of years to accept that I am really not and I truly believe this is where my anxiety is stemming from. I feel I got very angry at my ex following the end of the relationship and instead of telling people what really happened (we worked together and I didn't want to ruin his career), I let a lot of things go and just ranted about him as many exes do.
I overthink things terribly, assuming everything is my fault, I doubt my decisions and obsess over the silliest of things. I also feel triggered when I watch something on tv that has any sort of emotionally abusive scenes.
I'm at a very exciting point in my life and getting married to a wonderful partner this year. I have no doubts about this marriage or my partner but just feel like something is looming over me a bit (like I need to accept that I need to build myself back up or something). A lot of the time I feel embarrassed about the situation I put myself in and not being able to see it.
It's hard to pin point and explain. When I'm busy I'm generally ok but during covid (that's when it first hit me) and over winter when life is much quieter I really start to struggle
Anyone been in a similar position?

Just to add, I've toyed with the idea of therapy for years but never managed to bite the bullet and actually do it as I always think there are people out there so much worse off than me. I just fear my anxiety will continue to get worse if I don't address things 

Apologies if this is a bit rambled!

I overthink things terribly, assuming everything is my fault, I doubt my decisions and obsess over the silliest of things.

All these things point to lack of self confidence. How did you ex undermine you?

Yeah, all the time. Although all my friends and family told me he was emotionally abusive at the time I didn't want to see it. It's only since coming out of the relationship I've came to terms with it....or maybe I haven't and that's my issue
He was live bombed me initially. He was really narcissistic and very much gaslighted me.
If my fiancé and I ever argue now I can't cope, I totally break down and fear the barrage of abuse I feel is about to come my way.
I've talked to him a little about it so he's understanding but never go into too much detail as nobody wants to sit and hear you talk about your ex

Even responding to this now makes me tear up and get upset as I just feel it's all my fault so how and I should have seen it / listened to people earlier
I feel pathetic as it was years ago and I'm with such a good guy now yet I just can't seem to get past it

Nothing pathetic at all - on the contrary it's both brave and self aware to realise it and want to do something about it.

Therapy (probably privately) would help you but if that's too much to consider at the moment think of this; you are a good person who wants to see the best in people. This guy, for reasons that are not your concern, took advantage of your nature and tried to manipulate you for his own purposes. He failed and you got your freedom. That's it in a nutshell. He's to be pitied for whatever it was in his own upbringing/personality that made him that way but it's not you - it really is/was him.

Forgive yourself for your only shortcoming, which was to assume he was the good guy you knew as a friend, accept that you've learnt from the experience and let him go.

Thankyou @Eyesopenwideawake fir your kind words
I have private health care through work and have had a referral for therapy for a while now, just have never been able to pull the plug and book in as I feel like I should just be able to get over this.
I guess I just need to be kinder to myself and understand the way I'm feeling is valid. I do feel maybe offloading everything to a completely neutral party might help me accept and move on from this. I just want to go into my marriage as the person I was before and not let this fester in my thoughts any longer