The pain on back

I feel painful on back, the reason is Aiki... I'm not good at passive technique, so I can't turn well. I don't know what's wrong with me while turning, so someone noticed and looked at me, and showed me a good way. Our coach says that aiki is love. When we take actions, we need to think other person. We need to move as the river, not to stop the follows. That's very difficult, but I have to make effort.