Same thing happens to me if I'm not active for 3-4 days, I'm not sure how you managed to make it 2 months. Assuming you work a desk job, working out in the gym is probably the only thing keeping you flexible. You're most likely stiff as a board, which is throwing your joints out of whack.
Taking time off from the gym doesn't mean that you should become totally sedentary. Take up some other kind of hobby or exercise, and start stretching regularly.