I think he holds a torch for someone else?

Hi, I've been in a relationship for 10 months. I know he loves me, he treats me well but we've had a few hiccups along the way , he seems to hold on to his past. I was married until 6 years ago in an abusive relationship , it's taken a lot to let someone in again When I met my partner he was house sharing with a friend, a girl . I had no issue with this, one of my best friends is a guy I've known since we were kids, and this girl was never there she was always with her boyfriend. It then came to light that my partner had had feelings for her 3 years ago . They were good friends going on holiday together etc... And his feelings grew. He didn't tell me this until I questioned him after seeing old FB posts that suggested it. She didn't feel the same but they remained friends, going into a house share because her guy wasn't ready to commit and he says it suited them both. I found this odd on his part how he would want to or could live with her because of how he used to feel. I think reading between the lines she moved in to give her boyfriend a nudge, well it worked she left and moved in with him 4 months ago. She's never really kept in touch with my partner, but I've noticed how he moaned about this initially . He often brings her name up in conversation, moaning for example she's on holiday again. If we are having a conversation about something I've noticed he will use the term 'we' did this and 'we' did that referring to her. He told me today he texted her yesterday he said she didn't know about certain changes in his life. I said I don't know why you bother she hasn't bothered with you since she left. I guess my fear is that if things don't work out for her she will try and pop back into my partners life, that makes me feel threatened because of how he felt about her . I guess I'm asking for advice on how you would feel about this. I'm not prepared to be 2nd best to anyone . I know he adores me but the fact that her name crops up the way it does and that he contacts her now and again makes me wonder .hes a lovely guy apart from this, I just guess I feel insecure because of my past. Would you have an issue with your guy or girl wanting to stay in touch with someone in this scenario ? Or am I being stupid??? Thank you xx

Your BF's actions of referring to her in conversations and his use of the word 'we' tells you that he still has a connection with her. It really doesn't matter if she feels/felt the same way or not or whether she will come back into his life if her relationship fails...what does matter is that you need to make a decision as to whether you want or need to be with your BF of 10 months when it's plainly obvious that he still has and tries to maintain his feelings for her. Of course you're not prepared to be 2nd best to anyone, and you need a man who is capable of and will devote 100% to you to put you first particularly given your past. Your BF most likely won't be able to commit to you until such a time that he realizes that she's with someone else and he basically gets over her. There's no way that he can be completely 'with' you until this happens. Whether you're prepared to put up with this 'hiccup' in the meantime is totally your choice. Some woman would persevere with a guy as you have described your BF, while others wouldn't stand for it whatsoever. In reality, there's no way someone can commit 100% to another person when they are still hung up on a previous 'relationship'...but plenty of people do try.