Rejection from an avoidant man

I am 27F , I dated an avoidant on and off for 3 years.
Everytime he would give a lame ass reason to break it off , like family problems , financial problems and so on.
Last year , within 20 days of our breakup he started dating a new girl , who harassed me on a phone call when I tried to call him , UNAWARE that he had already started dating someone new.
Within 3 months , they broke off.
After that he pursued me twice and I took him back both the times. But he would himself cut it off after begging me to come back as soon as things would start to get serious.
This happened twice this year.
We came in contact again , and I find out that he dated that same girl again for 15-20 days before we spoke again.
I just found out yesterday , he even slept with her.
Btw this girl , harassed me to the extent that she contacted my family too just to get back at me.
She has an FIR on her from her previous ex.

So one day , we met and she saw us. She followed us for an hour after that.
His behaviour changed after that day , he did not apologise for the harassment caused to me again. Before this incident he was begging to make things okay but after this he just changed.
I have cut him off but I cannot get over his lies.
He always hid all the details of their relationship.
He always shifts the blame on me that it does not work because I complain alot.

Send help guys , I really need some perspective.

Love.