#mixup PLEASE HELP ME

hi my name is Brittney and I just want some advice I was in a 6 month long relationship with this boy Brandon I thought I had fell head over heels for this boy. until I found out he was an heroin addicted. so of course I looked passed it because the love I had for him was to strong. it went from trying to help him stop to him stopping coming around as much. as me and him were together I met his friend his name is Marco a long the time of being with Brandon. brandon got locked up and I found out he was cheating the whole time so I left him. his friend Marco and I started to hang out as friends it was nice to have male friend I could open up to about everything. as time went on I fell inlove with Marco and now me and him have been together for a couple months now I haven't been more happier in my life cause dating your bestfriend is wonderful. but Brandon gets out soon and all his friends are telling me he keeps telling them he wants me back and he misses me. And how disrespectful I am for dating his friend. I know shit is going to go down when he comes home and I'm scared of the results I don't want to loose Marco but what if Brandon makes that happen. what should I do??