Before I might "crack" the middle finger of each hand every few days, about 1 week ago I started noticing my fingers were very painful, as if the knuckles needed to be "cracked". When I tried to bend them back like I've always done it was too painful, so I "pulled" the fingers, (typically the middle fingers) and they would "pop" this way, but immediately they would feel again like they needed to be "popped". This is causing me to lose a lot of sleep because I'm in so much pain from this. What can be causing this?