you were doing great but when she came back all flirty you caved and had sex with her and probably said some stuff as well. This was probably just her ego seeing if she could get you one more time...not to worry I think you have done really well. A lot of guys in your situation see it as the end of the world. the fact that you have got up off the canvas and started seeing other women is great. Next time no marriage proposal except if it is from her and only after 2 years...