Tips or exercises to help with a low self esteem?

I was doing okay for a little while there. Then a few nights in a row I caught up with men (my ex came around because my health was really bad and I was worried I might need to go to hospital), then a male friend. Now I honestly feel so bad about myself that I feel like I can't leave the house. I feel ugly and worthless, I feel so self conscious I'm convinced people must complain about how hideous I am behind my back. I feel conspicuously unattractive.
I honestly don't know why. When my ex and I were together he used to occasionally say really hurtful things to me about my appearance (like that my friend had a 'better face' than me, that I should tone up etc etc) but this time he didn't say anything horrible.

Ugh. My anxiety is really playing up tonight. I'm feeling so paranoid that all my housemates are complaining about me. It's so childish. I have no reason to think that at all.