cheating

I cheated on my new boyfriend of 3 days, and I have no guilt nor do I care if he finds out. I feel like shit for feeling like this, because this is so unlike me. Since my ex I've became a heartless, numb bitch. What do I do..... I've never cheated. I like this guy that I'm with but unfortunately I don't see myself with him forever. 😞
I'm 21, I'm not a child FYI