A good chair makes a world of difference but they are hard to find.
So instead of Pilates you stretch out on bed? It helps me if the back hurts next to a hot wayer bag and the D3 helped as well although I replaced it for liver cod capsules.

Would it help to lose weight? You can also do inactive gym to strengthen the muscles. It can be done while you sit and even in bed (or if you walk). So multitasking behind the desk.

Take good care of yourself.