finchr is right. In order to make a conclusion needs to know how you feel before, during and after various movements.

However, based on the information you provided I would probably guess you have non-specific back pain, posture related. This is because from your video you look like you tend to extend your back a bit too much. When you stand / sit and use your arms, you should always think about sitting tall as if trying to elongate your spine skyward, not sitting straight. In terms of exercise, I would probably try 1) slow repeated flexion in sitting to the end of range or mild pain; 2) slow repeated trunk rotation in sitting towards the more painful side; 3) squatting against a wall with a flat thin cushion in between your low back and wall, keep the pressure of your low back against the wall during the entire movement. Keep the pressure just hard enough to prevent cushion from dropping, and try not to fall yourself too. Slow repeated movements, 10 at a time, concentrate on technique and how your back feels rather than how much you have done; 4) Heat and massage the paraspinal area to relieve excessive tension. Maybe even some cat stretching..

Thats just my initial thought. You really should arrange a physiotherapy session to analyze your problem before doing these exercise, if thats impossible then try it with caution, and do them slowly. Sometimes initial response is more pain, but your movement improves afterward, and become less stiff, less flare ups. However, if overall response during AND after exercise is negative, then dont do it again.

Good Luck