Should I feel guilty that I slept with a guy while on a break from my girlfriend?

Last night I went out with a guy friend an well I had a good time. I had too much to drink and had to stay at his place because I couldn’t drive back home. So he told me that I could stay over. While we were in bed one thing lead to another. Right now I feel kind of guilty because my girlfriend of nine and a half years and I are on a break. I feel like I cheated on her I want to know if what happened with me and my guy friend was ok. I still love my girlfriend so much and my guy friend doesn’t know about the relationship I had with my girlfriend. I still live with my girlfriend and feel like what happened last night should not have happened. I know I am able to do anything I want because she told me that we weren’t together anymore. She has gone out too and has stayed out till about seven in the morning last weekend and I don’t know what she does. For all I know she was with someone else. I just want to know should I feel guilty that I slept with this guy?