gosh, your thoughts are a bit all over the place. you have always wanted to move to the big city; well that urge will probably never go away. i think you should move and get it out of your system. you can always come back whenever you feel like it. it may be upsetting for the girl you're with but its just one of those things you will always regret not doing, if you dont.
as for your ex...you need to stop thinking about her. she's a cheater and in my book cheaters are nasty and selfish and they never ultimately change. also i'm a believer that 'you never go back' it's never the same, i live by this philosophy for everything.
Work like you don't need the money. Love like you've never been hurt. Dance like nobody's watching