Putting aside the sin issue for the time being.
Sweetheart what on earth are you doing with a person who treats you like crap off the bottom of his shoe?
He has said from the start he will make no endeavours to try and be with you.
What on earth do you want him for?
You have got to begin to love yourself, be kind to yourself, feel yourself worthy of so so much more than this.
Any guy who wants me, will have to move heaven and earth before I'll even notice him! Ain't no way I will ever chase after a guy who has told me he does not wish to be with me, that I am a convenient pass time till something better comes along.
You've got to really dislike yourself to think this is a person you love! I mean really, truly?
There are so many nice, loving, caring people out there and you're shutting yourself away from them and Allah, by throwing yourself at a guy who has not only no love for you in return but no respect either.
Remove/block him from your phone, email, facebook. If you can, put distance between you and him, go on holiday go visit relatives, if that's not possible change your routine so your paths do not cross.
And make dua for yourself, and do istighfar. Allah is Merciful, start praying five times a day, do nafl fasts if you can. Whatever, just start forgiving and seeking forgiveness, this hopelesness will not help.
I pity the woman who does end up with that guy you describe. He's not going to be nice to her you know.