I had a affair... advice?

So I work for the local ambulance service and My partner so happens to be my teacher from EMT school ( I graduated maybe 3 months ago). All throughout school, the sexual tension was through the roof, especially on clinicals with him. I’m in what I assumed was a committed relationship with a guy I assumed I loved ( you can’t love somebody then cheat on them..). 6 weeks ago, I had the worst call I could imagine. I won’t go into detail but I had to step back and ask myself if I wanted to continue to pursue my career. My partner held me while I cried after the call was over. One thing led to another and we ended up having sex in some run down hotel ( I know I’m the absolute worst human being.. ) and have continued doing so since. I told my boyfriend about the call and he brushed it off and told me to get used to it and stop complaining. I guess I needed comfort and somebody who saw and had dealt with the event I dealt with.. my partner is also married with 3 kids and I feel horrible. I feel like the scum of the earth, but I won’t lie and say it something I regret.. what am I uploaded to do? Quit my job and find another one away from him before even more toxic events transpire? Tell my boyfriend and deal with it? 
UODATE : I appreciate all the comments and I went to him with my concerns. He told me he was in the process of getting a divorce and even had the papers in his console of his truck.  I also told my boyfriend who then refused to end things and said we’d work through them. I can’t pursue a relationship with my teacher due to the fact rumors would arise and he could possibly loose his job. I’m at a crossroads right now even more.