Anyone else with bpd hate how little you feel you can trust your own thoughts/feelings?

I ruined a lifelong friendship a few years ago by arguing then blocked and ghosted from their life because I was so hurt. Immediately after it's like I had a brain block. Every time someone asked I just said I wasn't bothered, didn't miss them at all. I really didn't. It was like they'd never existed.

Forward 4 years and I start missing them. A mutual friend tells me they're still hurt, I feel genuinely confused. THEY feel hurt? So I think back over what happened, realise I was horrible, feel guilty and ashamed etc. It dawns on me that I push so many people away.

Oh and it was hilarious how for 4 years I kept saying to myself and others THEY were the one that had blocked me. 

Anyway this flip-flopping back and forth between "is this my fault?" "is it their fault?" and totally blanking on my own trashy behaviours is exhausting. I only ever see things on retrospect. How do we ever know what's real?