PLEASE SOMEONE HELP ME!

Okay well I been in a 8 year relationship with my boyfriend but something happened on Saturday that I really wanna kill myself and I feel so ashamed and sad and all those other emotions but I had un protected sex with this guy and also I was drunk so I didn't know what I was doing and now that I woke up the next morning and I fee like trash and feel horrible that i did that behind my boyfriend back and I never meant to do it but I do love my boyfriend but that's night I messt up please someone help me I need some advice!!!