so it goes, i too am sorry you are feeling so badly and bad about yourself. i can totally understand the feelings because i've had them myself. not lately anywhere as badly but i won't ever forget how i felt.
a thought-just like you did here, why not journal your thoughts in a notebook? it was recommended to me by my T during that time of my unbearable life. i felt it was a lot of hokum but he was relentless and followed up next time i saw him. so i did it. first difficult, later couldn't wait to write down how i was feeling. i found writing in the morning was best to start my day fresh and later as the day progressed. you could start before you go to work.
it won't take your worries/sadness away necessarily but you will find a thread of triggers and emotions that occur. i underlined mine later when i'd review what i'd written. then decide what is really true about yourself, your life,etc and toss the rest.
as for the person you feel badly about the way you treated them...if they are a true friend they will accept a sincere apology. i was taught to apologize when i had wronged someone and to not expect platitudes from them or even forgiveness. however i also know true friends accept us thru good and bad. i hope you can restore your relationship with that person.
as for other ppl we have no control over how they treat us or what they say. so be kind to yourself. who could do it as well as you? you are fragile right now. do something nice for yourself-even an ice cream cone if you like ice cream like i do. or whatever will make you feel good for that one moment in each day.
will keep you in my prayers. i'm so sorry you are experiencing this. we here at pc care about you. please keep posting if that helps too.