i need hella advice

so i drunkenly hooked up with one of my best friends new years <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> but the problem is he has a girlfriend (awful i know) but we kept sleeping together (i know seriously so bad) and i was totally fine with it being just sex and then he started bringing feelings into it and now im really falling for him like i was hanging out with him and his friend and couple days later he told me his friend told him that i look at him like i want him more than anything in the world and its a huge ass mess i don’t want to break it off because i think i might be in love with him and i don’t want to lose my best friend and he says he really likes me and i have no idea what to do