Tight hamstrings, a short lower back and the caterpillar pose

I have been trying forward bends for as far as I remember. Years with no results....I tend to lean back because my lower back may be tight and as I lean forwards, I get a back strain from arching the back. My hamstrings are also tight. I watched Bernie Clark's video on the caterpillar last weekend and have decided to change some things. Since a few days ago I have been sitting on a block with my knees bent and now I do feel the stretch on the lower back well. It's a better stretch. When I keep my legs straight my knees complain so I have to bend them. So far I have been holding this pose for only 2 minutes. It's already hard to sit relaxed in that pose. I think I will increase the time held once I get more comfortable. For my counter pose, I use the saddle pose. That pose itself comes with some challenges and modifications. I will blog about that later. I need to read another chapter of a novel before knocking off.