Is it normal to have mixed feelings for someone?

When I was a freshman in highschool I met this girl that I really liked. We starting talking and got a little closer, but over time she started to distance herself from me, then it was over. After a few months I got over it and moved on. I had zero emotion towards her, I felt like I was fully moved on. But... Now I'm a freshman in college. I haven't talked to her since. She has a boyfriend. I have no feelings towards her, until, I see her. Everytime I see her my whole body goes on meltdown. I start sweating, I get super nervous, and my feelings towards her grows. Then when I leave or she leaves the room. I go back to normal. Having zero feelings for her. I have no idea what's going on. Is this normal?