What Causes The Fingers To Bleed?

fingers bleeding happens quite often, different finger each time apart from my littles and thumbs, it dont hurt, blood just start to poor put for about 3 miniute or so.(comes from nail)
At first i thought i had a cut but i cover the finger with a plaster. but then it started happenin in my other hand and other fingers on first hand.
I have no idea why this is happening first time i noticed was after playing a guitar for first time, but i was using a pick. and that was just over a month ago. and it hasnt stoped.
Normaly when i lift somthing with the hand, sketch book, foulder or similar stuff, twise just when i was on a bus.