Have you looked into borderline personality disorder? One of the criteria is chronic feelings of boredom and emptiness. Another is involvement in self harming activities I cousin drugs or promiscuity. Another is emotional instability that rarely lasts for more than a couple of days. Also getting unduly angry at people.

I can't concentrate today so other people may be able to give you more insight into BPD.

Anyway I think your description sounds more like borderline but I'm not you so I can't know for sure. All I know is that you're having symptoms that are causing you distress. Best bet would be to get into therapy if possible so you can start to figure some of this stuff out.

Welcome to PC! I would say read some of the things here, and also visit the BPD forum to see if you identify with anything.