It’s long but please help me

Before my current relationship I was dating a guy for around a year, and we had sex. I never felt comfortable, he used to blackmail me and pressured me into doing so. Me and him broke up because he was nasty and whatever, and 5 months later I met my current boyfriend who I’ve now been with 13 months. I never told my current partner I had sex with my previous one as he would leave me. I always denied it as I felt dirty and like it didn’t count because I regret it happening and didn’t want it to. Please help me what should I do. I don’t want my partner finding out because he will leave me and I love him more than anything I can see myself being with this man forever. I’m so upset 😭