confused, love, cheating? affai? what do I want

I'm female and been in a relationship with a boy have been for 2 years I'm 19 he's 25 I love him he loves me, alls perfect well apart from I got talking to an old friend we were talking for years and it never went any further, I fell for her personality but I'm not fully attracted to her, my friends make fun of her as she's short and fat but tbh I see the good parts her eyes her smile. Anyway I got talking to her again just as friends but she said she couldn't do it as she finds me to attractive to not make a move on me. I fell for her personality again and can't stop thinking about her, I thought I'd be happy managing to just be friends but she can't do that and I want her to be apart of my life, my boyfriend does not want a family in the future and can't hold a job down but I love him so much and we both look good together I feel comfortable going out with him people think we're cute together my family likes us his family likes us, but if I'm with her I'll feel uncomfortable in public, my friends will make fun out of me, I just don't know, I feel like just leaving him and just going over to hers and kissing her I want her so bad, but then I think I've got a house and a life I can't just run away from it, I have a joint bank account with bills and shit

---------- Post added 12th Apr 2015 at 03:25 PM ----------

Oh and I keep asking her to hang out knowing full well she will come on to me, but I don't know what I'd do if she did, I feel like I'm putting myself into the situation to cheat but I don't want to hurt anyone I don't know why I'm doing this to myself, part of me wants to have an affair with her but come back home to my boyfriend and eventually of had enough experimenting with girls I'll be happy to settle down with my one guy, I don't understand why I'm thinking like this.

And to make sure my friends don't kniw how I feel about her I keep laughing to them saying she fancies me ahah like I'd go there! Then they all laugh along and we make a bit of fun out if her I feel so guilty though