So I feel quite silly writing this but the truth is my stomach is in knots and I'm feeling really low, so wanted to ask for your thoughts.
I'm in a new relationship (6 months). My new BF is the most lovely person; kind, loving, supportive, and very into me. He tells me he loves me, and more importantly, shows me he loves me all every day. I felt like I'd hit the jackpot.
When we first started dating we had those chats most people do about past relationships. Nothing out of the ordinary in what he said; a few long term relationships, just like me. However he told me about this girl that he is friends with that he developed strong feeling for, about four months before we met. He told me how he thought that he was in love with her but, the feeling wasn't reciprocated (he never told her how he felt but a friend of this girl told him that she didn't see him like that so he never told her). When he told me I was a little bit jealous but appreciate everyone has a past so let it go from my mind.
Last week there was an event which usually my BF and this girl would go to each year. My BF said he wasn't going to the first part of the event and, I took this to mean he wasn't going as he didn't want me to feel unsettled by him spending time with this girl (I couldn't go due to other commitments). I didn't say anything, I was just flattered he considered my feelings.
Anyway, the day before the evening part of this event he told me that she was going to be there. He said he hadn't know what to say and that's why he didn't mention it earlier; that he didn't want it to be an issue or for me to feel worried. For some reason the pit of my stomach flipped and I was really jealous/nervous. I tried to hide it but in classic girl style I went rather quiet for the rest of the day and said "I'm fine" a lot, which as we all know means the opposite. 
Anyway, off he went to the evening part of this event.
For contextual background my BF is the type of guy that if he knows I'm worried about something or feeling insecure he will do everything he can to make sure I know I'm loved and have nothing to worry about.
So, he is at the event and he text me a few times about silly random stuff but not once did he say anything along the lines of "yes she is here but you have nothing to worry about". I felt sick. It got to near midnight and I had worked myself into such a state I called him.
I told him honestly how uncomfortable I felt because I know him so well I know that usually he would have reassured me and the fact that he hadn't really concerned me. He said that he was sorry and that he should have text me to say that and that he knows if the situation was revered that I would have reassured him.
We then had a really lovely chat about how much he loves me and is so happy with me; that yes he was in love with the fantasy of this girl but the reality of her never matched up to what he had built her up to in his head. That I'm amazing and he has never felt like he does for me for anyone else.
I said to him "do you still fancy her" and there was a longer than perfect pause. He then said ".........not really, no".
Not the best of answers.
something in the pit of my stomach tells me that I have something to worry about. It's not her; as far as I know she has no interest in him, but what worries me is my BFs feelings for her.
If anything it's lust (his words when describing how he felt for her) but I don't want my partner to be lusting after another woman. I know it's normal to be attracted to other people even when you are in a relationship, but what bothers me is that he was infatuated with her, obviously is still physically attracted to her (just doesn't want to say as much as it would hurt me), and is in a friendship group where they will see each other at this event every six months (and is friends with her on social media etc etc).
How would everyone else be feeling. Am I overreacting? Am I being stupid. I want to think I am but I just feel so uneasy. It's shown me just how much I like him, and now I feel very vulnerable.
Any advice/thoughts welcome.
X