This!!! Heartbreaking in the extreme but with the most satisfying ending of anything I've ever read:
http://www.mangago.me/read-manga/senya_ichiya_shitone_no_himegoto/
Don't be put off by the art style. It's a beautiful story.
here's my drama list. and most of them, save from those that have bad endings or the ones i laballed as bittersweet are stuffs that can make you cry but have a happy ending http://www.mangago.me/home/mangalist/72632/
my unrequited love list also is mostly composed of heart-pinchers, just avoid those i labeled as 'ended with another'.
http://www.mangago.me/home/mangalist/57857/
Avoid the ones marked with

Hey guys, can you recomend me some heartbreaking yaoi manga that ended with a happy ending? Like, kue that fall in love with a married seme, something like that (=・ω・=)