What if I'm into my ex-boyfriend's best friend?

okay i dated this guy for two years but he treated me badly and cheated on me numerous times, so we then had a bad break-up but now, a year later, we are hanging out as friends and have put aside our differences. i met one of his friends about a week ago and i really like him. he pulled me aside one night and told me he doesnt know why but has fallen for me very fast in such short of time and i was so shocked because i felt the same way. he says no other girl has made him feel this way since his long term relationship and i feel the same. we have a lot in common and i get butterflies everytime i see him.. we are both stressing becaseu we dont know what to do about this. my ex, who is his really close friend, still wants me back even though we’ve been split up for a year. is it bad that me and him should even consider trying to be together some how.. i hate being so sneaky about having feelings for him. we sneak away from the group we hang out with all the time just to kiss when no ones looking and call eachother all the time but no one knows we even talk. i dont know what to do.. i dont want to get caught sneaking around but im scared of everyone’s reaction if we tell them we have feelings for eachother. because everyone knows my ex is still in love with me so neither one of us are ready to confess, we would break my ex boyfriends heart. just so u know i have told my ex many times that we will never get back together so its not like im giving him false hope while i have feelings for his friend. im so stressed out about this.. i think one of the other guys are already becoming suspicous!