I feel your pain. I do the same exact thing. Ouch.
Yeah, it's horrible! I actually successfully STOPPED for about 3 years after I finished uni, but went RIGHT back into it once I started school again. I'm going to blame it all on SCHOOL.
You are not alone...I detest my habit and I have the stubs to prove it.
Good to know I'm not alone! Right now the side of my thumb hurts every time I press the space bar. UGH. I feel so stupid but it's so hard to stop!