Looking for Some Advice

Hey guys. I'm a 17 year old senior in high school and I've really been struggling the past couple months with my sexuality. I could really use some advice/guidance/kind words. I am Roman Catholic and have been all my life so it's been quite difficult for me to bring to terms what I've been taught all my life with all these feelings and emotions. In fact, I was pretty homophobic until I got to high school and sometimes I even have this internalised hatred of myself and my feelings. My parents while not explicitly homophobic would be rather upset and disappointed if I tried to talk to them about this. I started to question myself in seventh grade but I would always find a way to suppress it. More recently, I have found it harder to do so. A couple of months ago my best friend and I came out to each other and we started flirting really quickly. A couple of weeks later when my parents and my girlfriend (now ex-girlfriend; we broke up for completely unrelated reasons) were out of town, I hooked up with him on three separate occasions that week end. I just feel so much guilt and sadness over all of this. I told him that I didn't want to see him anymore and while our friendship was kind of rocky the next couple of weeks, we made up and are friends again, but I still feel badly over the terms in which I told him I didn't want to see him. I told my sister some of what happened and while she was very nice about it she couldn't really empathise or offer any advice. If anyone has any advice on dealing with being religious and maybe being gay, I would really appreciate it.