Unamrried partners are a lot more difficult now since there is civil partnership laws in place. I know it is a sensative subject but fiancee/proposed civil partnership visas are a lot easier then the unmarried partner ones. Allibee21, is there any reason why you are chosing the unmarried partners route, and can't take advantage of marriage or civil partnership? If there is some reason preventing you, just collect as much stuff together. Don't forget that visa stamps in the passport are part of the proof, dated pictures, affidavidates from friends and family who know you have been together, etc all help. Just kill them with proof and hopefully you will get through the process. It is subjective. Can his parents provide sponsorship for you, that will help on the money side of things...
AddyLight, it is true that unmarried partnership visas are only available to those who have lived together for 2 years and can prove it.
I know faydra72, you have a struggle, and I know it is tough. There isn't an easy way except to get the divorce finalized. Love is blind and that is tough.