Hello and thank you for your question.
How long have you known the facebook girl and also how old are you and this other girl?
Okay and have you and this other girl talked about your feelings for one another or acknowledged that there is an attraction, etc. Are you currently in contact with her and do you have plans to see her. Also how was your relationship before this happened, with your girlfriend? It sounds like it was a happy one...
And what is your longest relationship been to date?
One thing that stands out to me here is that you admit to cheating on all of the others before this. You haven't physically cheated on your current girlfriend, but you have started another relationship while with her, in a sense. So, I do encourage you to really look at this pattern you have of going from woman to woman, and having trouble being loyal and committed. Another thing to remember is that a relationship of one year where you are living together, etc. is NOT going to feel as electric and exciting as someone brand new. Admittedly you do have a spark with the facebook girl, but at this point, that is based on lust or "infatuation" as you simply have not known her long enough to have it evolve into love. That being said, you could start to build a relationship with facebook girl and have it be the one that endures for you. I do need to caution you that as fb girl does not know you are living with a girlfriend, that you would be starting this new relationship with her, already without being honest with her. You have a lot to consider here. However you have already told your current girlfriend... so that is out in the open.
If the relationship with your girlfriend whom you say you love is great and you two are together, why throw that away?
No you are not "wrong" in feeling that way. And you are technically "single" meaning not married and certainly at any time can pursue whomever you would like. It is good that you didn't cheat and instead told your girlfriend the truth. It seems really the only way that you will know as noone can give you any guarantees is to do what is already in motion. It seems your gf is moving out and you will pursue a relationship with this new girl. I would go ahead though and let the new girl know (now) that you were involved with someone and that is ending. You don't want her to find out from someone else. And then see where things go with the new girl. But you will have to make a choice her and that is what is painful and also scary. Please click ACCEPT.... Thank you!