First time poster- anxiety over appearence?

Hi everyone. Sorry if this isn't in the right thread, I'm new.
I'm 18 and after experiencing a stressful exam season had put on some weight. I felt really unhappy with my body and so have been eating healthily and doing more exercise (11st 8 hoping to reach 10st). However, I think this has lead to an obsession with my appearance. All I can ever think about is how fat/ugly I am, if I'm losing weight, what I need to be eating, to the extent that it keeps me awake at night; I literally lie and stare at the ceiling making lists of everything that I hate about myself.

I'm going to university in September (moving from the north of the UK to London), and all I can think about is how people will react to the way I look; that no-one will want to be friends with me or date me because of my weight and looks, that I'll never have a boyfriend and be forever alone (further heightened by the fact that friends all around are gaining boyfriends whereas I've kissed one person and that's about it, and 'talking' to guys has never lead to anything).

The worst thing is that I know this is stupid, and I can hear myself in the back of mind telling me to grow up and sort myself out, that this is such a stupid, vain existential problem. But it's keeping me awake at night and making me miserable.

Has anyone ever experienced this way of thinking themselves, and how do you battle it?
Thanks guys, just needed an outlet.

A lot of guys say they prefer a woman "with a little meat on her bones." I think you will be just fine at the uni. Immerse yourself in your studies, join some groups, and instead of making those lists, try reading some books about how to boost your self confidence and self esteem. You are a worthy individual with a lot to give in this world!