Suspicious of fiance and a girl

My fiance (then bf) broke up with me during a very stressful period in his life last year. During this time, a mutual friend of ours who did not know we were in a relationship talked to me a lot. Let's call her Emily.

So Emily and I were coworkers during this time. She was single. She told me that my bf/ex had asked her to go for lunch, though it could have been more of a "let's hang out and catch up" sort of thing. Either way we were broken up so I tried to not care. It sounded like a date to me.

Fast forward a year and we're engaged. We are seeing a counselor for a problem he has that made me lose trust in him (not cheating). Things are much better and I really do love him. However, he is secretive around his electronics and will rush into the room if he left his laptop unlocked and I happen to go in to get something. That's just one example. We also happened to bump into Emily at the airport and when she saw that we were together, she got really uncomfortable and didn't want to talk. My fiance asked if she wanted to have lunch with us since we both had a later flight but he seemed really enthusiastic. She was even more uncomfortable and practically ran away.

Today he was on his laptop and I went in to get paperclips. He was acting weird so I intentionally hung around longer and chatted. He got a message on FB, I asked casually who it was, and it was Emily. I haven't thought about her in a LONG time. Now I am just suspicious all over. Ladies, please let me know if you think I'm crazy or if there really is something fishy going on here!! I don't snoop but if I had his password, I would :(