Should I be worried that my boyfriend have a thing for my now ex friend?

Me and my boyfriend have been together for over a year, I never cheated but wasn't the best girlfriend I could've been but I would cook for him and clean his house I was there through alot of his troubles and he treated me like his wife I wanted to wait to get married. I'm 25 and he's 31 divorced with two kids I have never been married and don't have any children. About three weeks he started changing a little 1st he changed his facebook status to single, then he said he was having a family reunion but was inviting his coworkers and if i didn't like it not to come, I asked him if he wanted o take a break he said no he wanted to work it out, a few days later we went out with a friend of mine and she kept talking about my outfit like why am I always matching she acted like she hated that I was dressed up she's a big girl who wears skimpy clothes not at all attractive and gets mad when smaller women get the attention.she was going out of her way to laugh and talk to him which I didn't mind we go in the club and he ignores me to talk to her. I go to the bathroom and get a text that my best friend died I ran out the club crying he eventually came out but I told him to leave me alone. He goes back in I eventually go in and he comes up with her and one of her friends following him. She stays away from me like she's guilty of something. My boyfriend and her kept whispering to eachother then I asked him what was going on he said I just hated they were people persons and he didn't wat to leave till she left. He then wanted to go upstairs to her apartment to use her bathroom. We had a argument after that and I dropped it he then emailed her on facebook thanking her for the night and she sent him her number and he friended her and blocked me cause I unfriended him. The next morning I asked about it and he and I got into a fight I broke up with him and we didn't speak for a few days. We made up but he ended up saying she reminded him of his ex then I asked if he was talking to her he said no he hadn't spoken to her since that night. I found out from an email from her that they had spoken and he finally admitted it but said he only talked to her to ask her if she hacked his email account. We are trying to work on the relationship but I don't know what to do. I think he still talks to her or is interested in her I'm suppose to be leaving for the military soon. I need o know what I should do about us first.