How do you know... leave, stay...?

I liked this guy at work for almost a year and we always flirted with each other and bumped into each other then started a casual relationship. In the beginning we both saw other people then somewhere along the way we became exclusive everything was great we made all kinds of plans together and always talked about things. Everything was perfect physically, mentally and and most of all emotionally. Then I got pregnant... He cheated on me when I was pregnant (IMO if you get someone pregnant and are still with them you are exclusive although we never said that out loud). Every since I had my daughter things have not been the same we have some awesome moments but for the most part things aren't nearly as good as they were. I love him so much and think about him all the time but I don't know/ feel like he thinks of me that way any more. He joined the army right before I had my daughter so he has been gone most of the time for this last year and is now in Iraq so we cannot see each other and I want to know if he will still want to be with me when he comes back. He says he loves me and I'm the most important thing in the world to him and so is our daughter. But he is always short with me when we talk and pissy. Is that from being in the army? But he started getting distant when I got pregnant before he joined the army. We went from working together, working out together, eating together, everything together to 5-10 min phone calls everyday. I know I will wait until he comes back to make any decision because I can't send "dear john..." letter and babies need their daddys and I love him but I feel like he isn't concerned about us and I think he is cheating on me, more of a feeling and "misunderstandings". He sent a girl an e-mail and asked for her phone number... she does work in the finace office but she said that in her e-mail and she thought he was being flirty because she told him "I thought you had a girl friend" he said he wasn't and he wanted to know about changing his something or another and she is in that depatment in the army and plus he told me "if I was going to cheat on you why would I ask you to check my e-mail" Am I being paranoid because he cheated before or is he now?