I can think only at this one right now
http://www.mangago.me/read-manga/junjou/
it's pretty long but a good read ^^
And something similar would be:
http://www.mangago.me/read-manga/cello_mellow/
( in this one of them is on the lookout for a girlfriend and the other one is jealous if I remember correctly)
http://www.mangago.me/read-manga/a_spectrum_of_emotions/ (more like a misunderstanding but it creates a little jealousy and it's a cute story)
http://www.mangago.me/read-manga/non_tea_room/
http://www.mangago.me/read-manga/kimi_ga_koi_ni_midareru/ ( jealousy for both, seme and uke )
Well, I wasn't a great help but this are some good read if you want to give them a chance. ^^
can someone recommend me a yaoi manga where the uke or the seme have an ex. girlfriend or ex. boyfriend that intervening in their love life and one of them (seme,uke) get jealous, or something like that...