I'm a 19 year old male with low self esteem. I've always been very closed off about my feelings and problems

A few nights ago I talked to this girl I know about my self esteem issues for the first time. We talked for hours and she told me time and again that I was a great guy. She told me I was attractive, and have a great personality, etc. I really started to feel better about myself by the time I woke up the next morning.Now, though, I can't stop thinking about her, but I leave to go back to college in a few days and I go to school 4 hours away from her. So now I feel constantly depressed because even if I told her how I felt it wouldn't matter. I feel helpless and I don't know what to do.