One day someone talks to me and I think they must love having me around and I feel so secure and happy, and then the next I wake up in the morning hating myself because what if I said something that made them stop liking me?

I get this urge to distance myself from everyone I know because I decide that they must have realised how much happier they are without me and they're never going to talk to me again.

I've started trying to tell them about it, or even just start conversations, but a lot of my mates take a while to respond, or don't at all and it makes me feel horrible. 

Any exercises or anything I can do without reassurance from other people to make myself feel better? I don't wanna be this person anymore, I just wanna not care anymore.