Dear Marie:

You are welcome. Sitting for too long does hurt our lower back, so it is recommended to get up every so often, walk around, stretch, before we sit again, and see to it that your chair is comfortable. My additional recommendation, from personal experience (if you are not doing it already), is  that as you sit-  shift once in a while right and left, so that the weight of your upper body is on the right side of your bottom for some time, then on the left.

Reads like you’ve been doing all you can regarding the maintenance of your apartment. I think it will be the responsible thing on the part of the owner/ management, to give you a rent discount for all the trouble you are going through.

anita