A very common pattern I have seen with people when they mistake excitement or passion with love. Anyone would be happy when you are traveling to other countries and being at lovely resorts. That is not love. If you want to know you are truly in love you gotta do something mundane and boring with that someone that you normally do with yourself. If you can enjoy the boring and normal stuff together then its a good sign. Relationships is not all lovely, it requires compromises and adjustment. Apparently even though you being at 20 behaved maturely, the girl obviously didn't.

You got a life experience out of this. It is an opportunity to learn. Get professional help and everything else will be fine.