partner keeping in touch with ex....please help me

i posted earlier about problems with my fiancee and things between me and him have improved soooo much and very happy, and now i face this issue and i really dont know what to do because we're trying to make our relationship work. the problem is well i was trying to check my "myspace" mail and when i went to the page i was browsing around and i noticed that it wasnt mine but it was his, so i was curious as to how his page looked like and everything, lol plain as ever, anyways i seen that he had sent a message to his ex-girlfriend asking her how she was doing blah blah, this is the girl he has been with for two years....this wouldnt have bothered me if his relationship wasnt that long with her, supposedly she cheated on him and so he broke up with her. well this he didnt tell me, but the a month before this he told me that she had requested him on her myspace friends list and he said that he didnt have a myspace, so he came to my myspace and replied back, but he told me about replying back to her from my page which i was glad he told me about it. we had a talk about her when i replied back from my page, he said that she has some issues from her past and he told me that he reminded her of her dad, so thats why it was hard for her to let go whatever that meant, he also told me that he doesnt see getting back with her, but he tells me he's not going to ignore her if she tries to communicate, my fiancee and i have been with each other 4yrs with 2kids, just so you know what would be at stake, ok back to the story, anyways i was ok bc he made it seem like she was saying hi to him for the very first time...to everyone's knowledge, awhile back i came across his emails from the two of them by accident (i swear) this is when our first was about 6mos old anyways they have been keeping in touch talking back and forth trying to have a date for coffee at starbucks, when i first discovered this i was upset, but i rationalized it out that if he was going to be with her he would've despite reading the statement that him and i were not going to be getting married due to our issues were having...also keep in mind that when him and i first got together i received a phone call from my ex that i had dated for 6mos to wish me a happy birthday and he flipped out about it, and told me to tell him to never call again bc were are together, (sounds like a hypocrite) and it was disrespectful for him to disrupt our relationship, while he's been keeping in touch with his ex of two years,

well ladies and gents i really need some insight because i dont know how to feel towards him anymore. please help Tweet