I cheated on my boyfriend with my ex

Hello,

I cheated on my boyfriend with my ex, who I broke up with 2 years ago. It was stupid and I regret it so much. We happened to be in the same bar and after the bar closed he offered to walk me home and I just wanted to talk about a few things that were left unanswered and I just wanted to hear his side of the break up. One thing led to another and here we are, in my bed. We always had crazy amazing sex, he was actually the one who taught me how to get pleasure from it and helped me to get to know my body.

Now the guilt is killing me, I constantly feel like I'm gonna have a panic attack. Anxiety is through the roof. But I know that I can never tell my boyfriend and stay in this relationship. He would never forgive me.
What makes it worse is that sex was unprotected and I'm scared that I could have got something from the ex. If I did, my boyfriend will know for a fact and it would destroy us 100%.

What do I do? How do I deal with the guilt?

Because right now it feels like this feeling is going to destroy me from the inside.