Struggling with past mistakes.. stories or advice please?

Okay, long story short when I was 18 I had my “ glow up” and liked attention that I never used to get. Nothing crazy. But I ended up being in a theatrical show. At the end cast party everyone got really drunk, and I ended up having basically a 3 some with two guys who were older than me. It was a mess and it wasn’t protected given that we were gone .And for the past 4 years I can not let it it go. I got tested a few times and luckily I never caught anything. I never did anything like that again. But everyday I wake up so disappointed in myself and I feel like an awful person and it really really makes

Me upset because I know if my parents knew they would be so so so disappointed in me. I feel so gross. The sadness and guilt I have over it has made my current relationship really hard too. I’m sorry if this all sounds stupid. But I just don’t know how to live with myself :( thanks for reading if you did!