What is the best way to start things back up again with an ex with some trust issues?

Me and this guy dated for about a year and 3 months; we argued alot during the last month and didnt have the best breakup back in early December ‘08. I called for a break and about 2 weeks later, he didn’t want “committment”...so i started to move on and i suppose he did too…around my bday in late Jan we started talking about getting back together and have been on and off talking about it since then. He still talks with his other ex alot [dated her before me]. He doesnt have ANY feelings for her what so ever but it drives me crazy when she texts and calls him all the time either to hangout or just for conversation. He hooked up with her while we were on our break and i did the same with other guys…so i guess we just have some trust issues. We both still really care about eachother and tell eachother all the time but when we get SO CLOSE to dating again, something stupid happens[whether it be plans not working out to meet up or over his dumb ex gf]....Help!....thanx<3