Unable to sleep properly & panicked. Do?

I'm facing sleeping issues from last one week.I'm only sleeping for 3-4 hrs daily & that also not properly.I try to sleep a lot in night but fail.I get irritated, upset, angry & crying at very little things & feel low & like I am overthinking most of the time.I've recently resigned from my job.That was my own decision coz I wasn't feeling good in that workplace.Right now I am unemployed & in home only.But it's not like that I keep thinking about being jobless all the time.There're so many things running in my mind at the same time but none of the thoughts are fully formed enough to express out loud to anyone.I try to do my studies, read books, do painting (that's my hobby) but unable to focus at anything.I feel like staying alone all the time.I don't like to pickup any calls from anyone.I don't know any exact reason for feeling this way but I'm worried about this.This all has started happening suddenly.A week before everything was fine.Please tell me what's this and what should I do??