Is it ok to be fantasizing about another man when married?

hi, my husband & i love to party and a few weeks ago we went to a friend's house which she shares with her boyfriend. we had a barbeque, were drinking. we continued indoors (just 4 of us) we took shots, listened to music all that good stuff. anyway at one point in the night my friend & i were in the mood to spice things up a bit for our men so we changed into tiny shorts & our bras. that was fun for a while (we danced with them, me with mine and she with hers) then im not sure how it happened but we stripped our bras off and dropped the shorts. so we danced around with nothing on but a thong. it felt so comfortable & our men did not mind. i think it made it easier cuz we both had similar bodies, both a size US 4 but my backside is bigger than hers. at the end of the night as we said goodnite her bf surprised me by touching my but i didnt think anything of it until the next time we partied together.. he's been giving me more attention and he always seems to take a chance to touch me, basically flirting. since he's hot i couldn't help it & started fantasizing abt with him. its driving me crazy bcz i never thought that before & now the thought of sleeping with him is stuck in my head & i cant stop playing out scenarios of an affair. the thing is we hang out with these pp all the time & planning a trip to goa together & although i would never cheat on my husband ive been seriously considering suggesting a swap during the trip. is this crazy? my husband & i are so in love & he is always trying to have with me we do it everyday. i think its too much sometimes but im so used to it now bcz he cant stop himself, he says he finds me too y he cant help it. we like to experiment sometimes & a couple of months ago i slept with a girl (my 1st experience) as he watched. that was not for me.. i didnt enjoy it. but it felt good that we did something crazy & nothing changed between us at all.. it was a good laugh but thats it. the last week id sometimes fantasize abt my friend's bf during what is the best thing to do? i feel so tempted but dont want to **** everything up!