Cheated and idk what’s next...

So I’ve been with my boyfriend for about a year 1/2 and I’d say our relationship was good until recent. He’s 20 and I’m 17. I’m still in high school and still have my senior year to go. The sex is good but I’ve been getting bored like idk i wanna experience someone else. I feel like we rushed into everything so fast. He was my first btw and I haven’t been with anyone else but him until recently. I cheated on him with my guy friend. We have a class together and he’s always flirting with me. One day mention to me that he wants to have sex and he’s asked me this before but I always thought he was joking. I don’t really know why I said yes but I said yes. Not to mention that I did have a crush on him in middle school and some of high school. We had sex I told him that we can’t catch feeling and this was only happening once. I cheated on my boyfriend for my own selfish reasons and I feel really bad. Here’s where I get stuck I can’t tell my boyfriend bc I know that he wouldn’t be able to handle it. And here’s where I’m also stuck in started to have feeling for my guy friend and idk what to do!! Let’s just say that I cheated bc it was just lust and well they are both completely different in the body types my guy friend is more in shape then my boyfriend. What do I do I hope that I get more advanced from people then hated on bc idk who else to ask and I can’t tell people bc well I just don’t want it to get around school and have some one tell my boyfriend.