Thanks, you were right all along. Just side plank for 30 seconds and 3 sets did fix my problem. More focus on pelvis and abdomen while walking or standing. Maybe adding relaxation ball would be good idea but i feel like my problem is already fixed.
I have last one question about deadlifts, mostly about focusing on hamstring. Can a very tense harmstring with a poor range of motion cause the back to take too much work? Should I mobilize harmstring and take care of the range of motion. If so what level should I get. Yes i work on computer a lot