<human>: so already i've painted myself as something of a 'bad person'. anyway, i'm all sorts of turned around in regards to this. my feelings all started about six months ago. i was struck quickly by the fact that i had romantic feelings for him and was summarily disgusted by how i felt, and felt as though i was betraying my friend. cut to january. she goes back to her home town for eighteen months to take a break before she goes back to school, and her boyfriend and i are still in the same city.

i've always felt really comfortable with him and we always just tended to get along with each other. so we started hanging out essentially every day, just kinda spending our time together rather than so much 'hanging out'. then about a month ago he presented the idea of sleeping together. i'd spent this entire time trying to suppress my feelings but i'd been fantasizing about this happening for months so i ended up doing it.
we established in the beginning that this was just for fun and he wasn't going to break up with his girlfriend or anything since they've been together for three years and had more or less 'settled down' in a sense. and after a while of talking and sleeping together he admitted that if things were different then we'd be a couple. and i thought this would make me happy, knowing that he feels that way about me. but again, he won't be leaving his girlfriend. i don't want to end it, because i'm enjoying it too much and i've never felt more comfortable than when i'm laying in his arms. but at the same time i have to accept that this is only going to end in heartbreak for me. i also care a lot about my friend and their relationship a lot which is why i want to keep this so secret.

so what do i do? i don't want to end it, but i'm also sick of having him on my mind all the time when we aren't even dating.

Can you condense the text into a few key points?
<bot>: sleeping with friend's boyfriend, also in love with him, he won't break up with his girlfriend. i don't want them to break up, but i also want to be with him myself. what should i do?