<human>: Could you distill the essence of the text into 1-3 sentences?

All right... let me try to explain this in as little time as possible. 

Andrew had been dating Katie on/off for ~8 years. He and I met last February and have had a pretty spectacular relationship. The only issue I have with us is that they two still talk. He never tells me when they hang out and I only find out when she leaves something in his car, or, recently noticed her foot prints on windshield. He never tells me when they talk, but I know that they text frequently. He still goes on her facebook, likes her things, etc. Tries to hide the fact that he helps her out (couple of months ago, he had to bring "someone" to the airport- I asked if it was Katie and he apologized for hiding it). He still has some things from their relationship, but not much... 

I just get upset when she knows that I'm with him (texts him the night of July 4th) and deliberately leaves things around so I find them. He doesn't think anything of it and reassures me that he doesn't have feelings for her but I don't know. We've both cheated in relationships.

We're both trying to figure out how to communicate better, because both of us hold things in. We've had talks about this before, and I've told him how I felt as if there isn't a whole lot of room for me in his life when I feel like I'm sometimes competing with her. And that no matter what, she will always come first between her and me because of their history together.  

I feel guilty for hating her, feeling jealous, and insecure. He's terrified of losing me, and me cheating on him. I'm leaving for a week later this month and I have no doubts that they two will be hanging out together.
<bot>: boyfriend of 6m frequently hides talking with his ex, I'm extremely jealous of this and I don't know how to effectively communicate this to him. I feel bad for feeling this way.