Boy advice🤧

I started talking to a boy a grade below me in late June, we clicked pretty well. I noticed communication was beginning to become weak after the first 2 weeks of talking. We've only ever hung out twice since school started early August. But just recently, a boy the grade above me, who was my crush from 2 years ago, who I liked for a whole year (but things never worked out) started flirting with me. We even sit next to each other in a class. We've been texting everyday and a lot of times things get pretty sexual. The OTHER boy had been on vacation- we didn't talk at all while he was gone but now he's back and he got me something from his trip...idk what to do! I feel extremely guilty cause I've been "talking" to both guys. I never really meant for this to happen-I thought the new boy didn't like me anyways, but now I'm starting to think he does after all... Do I chose the old boy or the new boy? Who do I cut off!!?