<human>: Give me a shortened version of the text

My girlfriend and I have been together for a year and a half and everything has been sweet (however not without the normal argument here and there), and she was soon meant to be travelling to another country for work for a few months.
 
She had been planning to go and live with a friend of her friend X for this time, and had been telling me that she had been making lots of plans to see X when she was away and she was glad he would be nearby etc. 
She has mentioned X a fair bit when we have been together but I have thought nothing of it due to him just being a friend, indeed when we had been together for about 2 months he came and stayed at her flat (in her room) for a week (but X and I were kept apart). 

She told me just over a week ago that she had been with this guy for a few months a year before I met her, but they had stopped seeing each other like that. She told me really reluctantly, and after I could see that she was keeping something in a related conversation and I had to ask several times for her to tell me. 

She's now not going to that other country for a variety of reasons, but I believe I'm one of them. Whenever I bring up my concerns she says she understands, but tries to bring up her worries that I have feelings for other people when I'm at work or on a placement somewhere (I've introduced her to everyone I know and when I'm away I'm glued to my phone to her, and regularly have her to visit). I don't think these things are really comparable... Me being away on work versus her having an ex stay in her bedroom...

She's a really great girl, extremely supportive and I had had no reason to think that we weren't completely in love etc. It's just a bit weird.

Would I be an idiot to believe that nothing happened when her ex came to stay in her bedroom for a week, and similarly that she was going to go and stay with her ex and hadn't told me that they used to be together?
<bot>: Girlfriend's friend turned out to be her ex, he's stayed in her room and she was planning to go stay with him until i found out they'd been together. Is trusting her word stupid?