knee stretches?

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?

Im not an expert, but as far as i know you have to be very careful with your knees. When im doing stretches for the rubber guard i make sure im stretching my hip flexors. When i first started stretching i felt pressure in my knees, but now if im stretching my left side rubberguard i will open up my left leg more (so that my left knee is further away from the midline of the body), that way it stretches the hips instead of the knee. I also hug my knee tight while im stretching, i feel that it isolates the stretch to the hip flexor aswell.
i hope you kinda understand what i mean, i suck at describing stuff
Some more experienced dudes on here should probably be able to help you out more.

hey man, Corey hit the nail on the head about focusing on the hip. you should never stretch your knees buddy, when you stretch ligaments and tendons they becoming weak and you can seriously mess up your knees, your knee is a hinge joint like your elbow, so you should always keep your ankle in line with your thigh.
"stretching your knees" as some people say isnt actually stretching the knees as all, but the hips, mostly your abductors, adductors, hip flexors, glutes, hamstrings and other muscles around your upper leg/ass.

if you are gonna pull your leg to your chest to stretch, make sure your knee comes across your body and doesnt stick out, you tense your foot up to stabilise the knee more and never pull the ankle/foot, the pressure should be on your thigh/knee.
hope that helps man :D

P.S. i'm not a pro or anything, this is just what i've gained from research and experience.

Thanks for all the tips guys!

Knees already have full range of motion, hips do not. the only thing that limits knee range is leg muscle/back muscle tightness (these are the ones you stretch when touching your toes). Stretching your knee is analogous to loosening the hinges on a door, sure your increase its range of motion, but not in a healthy way, and this is what will lead to weak knees. Just keep doing butterfly and/or full lotus and your hip mobility will inevitably increase.

Thanks for the help guys. I'm seriously glad that I asked for advice because I was stretching my knees really hard and clearly doing the wrong thing. Hopefully they will recover from what I have already done.