I've been doing some pretty serious stretching every day for the past few weeks and it's been going good but when i pull my feet up to my groin to stretch my knees they hurt. At first I just thought it was probably because they were tight but at this point i think that it's doing more harm than good. I stopped doing them because it seriously hurts and i don't want to injure myself. Has anybody else had this problem or know if there is anything i can do?