She slept with someone else and it hasn't even been a week.

She slept with someone else and it's someone I have to work with. I'm at work rn and have to see this person and idk how to act. I wanna rage.

I found out because I'm an idiot and had a suspicion and went over to the guys house and saw her car there. I know it's wrong, but everything is so fresh and I feel like I'm losing my grip on reality. Help