While I am not here to diagnose what is causing pain or discomfort in your forward folds, I will give you some options that have helped troubleshoot this pose for me. First things first - (despite what you may see elsewhere) you don’t have to get your torso laying flat over your legs. AND no yoga pose should ever cause you pain… some poses may be challenging, but if they are painful we need to troubleshoot that pose!
The following options depend on where you are feeling the discomfort/pain in your forward fold.
If you are feeling it more in the middle of your hamstrings, try bending your knees as you come into your forward fold.
If you are feeling it more in the sit bone/hamstring attachment area, don’t fold so deeply - stay up higher. I find using a block helps me not go so far. Also make sure your weight is evenly distributed between your feet. Often when we are sitting too heavy on our heels this pushes our hips back, putting more pressure on the hamstring attachment area. So even out the weight- from toes to heels. As you do this it should help shift your hips more forward over the heels instead of pressing back behind the heels.
Hope this helps!
Let me know what other poses or transitions are causing you discomfort and pain and I’ll try to troubleshoot them here!
As always, this is just my own opinion based off of my experience and knowledge at this time. There's always more to learn and consider. Not all poses work for everyone, so please honor and respect your body and do what is best for you.