I 28F was in an 8 year long relationship with my mums older third cousin 51M.

Okay so for context I (28F) and my mums cousin (51M) were together for 8 years. We split up 2 years ago, my decision and ever since I have this deep shame and disgust. When we were together he was super manipulative and controlling and deeply impacted my mental health. I relied and depended on him so much because he isolated me away from everyone else including some family members. He also had 3 daughters around my age so obviously i was kept his dirty little secret for all those years from them. Since we split up though I have moved on and met the most amazing man who adores and loves me so much and has showed me how badly I really was treated the only thing is I haven't told him about my past relationship. I told him I was with an older guy and he didn't treat me so well but not the fact that it was my mums cousin. I'm absolutely petrified off losing him but having the weight off all this is really affecting my mental health again. I want to be open and honest and explain it all to him but in reality what man is gonna stick around after hearing this especially as we've been together a year now. I just dont know what to do or how to even approach it. How would I go about bringing this up to him without him thinking I've betrayed his trust or dont trust or care about him enough to tell him? I'm at a loss