Should i make it with my cousin or stay with my fiance?

Ok so i dont need judgment on the situation this is all legal!! Basicly my cousin came over from australia nov 2010, we met up after not seein each other for 22 yrs (he lives in Oz),so all grown up now, teenagers then!! (im 37 he's 35) His mum is my dads half sister we share the same nan. We bonded so well, done very similar things in life, been through similar things but want the same things in life. Weve been out and spent a lot of time together alone since he's been here, weve spent nights together alone on the sofa whilst my fiance slept upstairs or was at work on nights, weve totally opened up to each other and obviously gone that step further and slept together which felt amazingly right. (i dont sleep with my fiance say only every 3 or 4 or more months) my cousin goes home on monday but plans to sell his house and belongings and come back here to live far away from all the family basicly live in secret. I'm totally in love with my cousin, we have such a good bond and i trust him, theres not much trust in mine and fiances relationship! weve been through so many things over the last 6 yrs, I do love him but i feel im no longer in love with him.(He's also 7 years younger than me) So anyway my fiance has caught my cousin and i kissing but still wants me and him to give it a go. He has slept out in his car the last couple of nights because he wont sleep here at home whilst were split, i dont mind if he did sleep here at least its not in a cold car and safe here, but i cant change that no matter how much i tell him. I miss him so much and not sure if thats just because im used to him being here!?? i want to be with my cousin but not sure if im making the right chioce!?? i keep thinking i should try (but i know it will never happen) forget cousin and get on and try harder with my fiance?? Or should i try get over the loss of fiance and go for it with my cousin?? If it makes it easier for u to imagine dont think of my cousin as a cousin but as someone u have fallen in love with so much and feel such a great bond....the love of ur life...ur dream women/man....everything feels perfect when ur together....nothing can come between u, but u have a husband, wife, bf or gf that has not been great for a long time but u feel u need to stick with it because thats what uv done for the last 6 yrs of ur life!! what would be right to do???? Please help me, im a grown women but have stopped eating and taking care of myself because of this, just 6 months ago i came out of a very bad depression due to life happenings and suffered agrophobia (fear of going outside ur home) i feel im fallin back into this awful illness and its the last place i wanna go, i feel so torn. my hearts breakin. Dont get me wong i know i prob deserve all i get with how iv treated my fiance and i should know better but i cant predict the future and didnt ever ask any of this to happen, i would never believe it myself, i myself would prob think it was sick just because its my cousin, but it did happen and everything happens for a reason i believe so for some reason this was supposed to happen i just need the help and guidence to see what i really should do next, no matter what my wrongs are i still need help and thats what im asking from u please. :-)(-: very mixed up...Faith.