Noticeable Hairloss at a Young Age

I'm 19 going on 20. I experienced considerable hairloss this summer due to stress and bad eating and sleeping habits. Maybe it will grow back, maybe it won't. I don't know. But I have to go to college in a few days and...

I am worried about gossip and mockery. I am worried that my reputation as a handsome guy will start withering away. Girls might reject me simply because they don't want to be seen with a guy like that. As in I won't even get a chance because the moment they notice the thinning, they'll think "No way", and that will be the end of it.

It is not too bad; I have no bald spots for the time being. But a taller person could clearly see the thinning at the top of my head (mostly the crown) - which are most guys - and a shorter person could see something strange going in with the ratio of follicles around my temples - which are most girls. The neon lighting and the seats at my college will contribute to everyone noticing.

I am not into the bald/balding area yet, but I'm getting there. In other words, I am not at a stage where I need a combover or a buzzcut; shaving my head would still be counter-intuitive, as I still "have hair" and it looks good on me. It is just visibly thin. And it annoys me. I'm sure people can tell. Especially around the temples.

Again, I am not worried about meeting people outside of lectures. I am just worried that my fellow students, mostly girls, will notice it during lectures, and dismiss everything attractive about me on that one premise.
Should I sit in the back where no one could see? Should I change my hairstyle so it is less visible, or disregard that and just go with a hairstyle that looks good on me?
Or should I take it to them, and instead of waiting for someone to gossip/comment on it, state it out loud?

This sucks. My ex and her friends are literally in the same class. I remember her stroking my hair and saying how good it looked. Now I imagine her thinking "Lol, omg, good thing I left him in time. He looks worse than Daniel Craig now. And he's not even twenty"... even though a huge portion of the stress that caused it was inspired by her actions.
And one of her friends actually played a role in us breaking up; this "friend" triumphs in seeing me in woe. So I can just assume she will spread the word and my reputation will plummet.


Help?