Constant neck/back pain. tried sitting sideways but no help. should i take breaks to stretch on the floor?

Make a change: If your spinal pain is constant, then simply changing your sitting posture is unlikely to get at the root of your problem. Of the many causes besides poor posture and physical deconditioning are inflammatory arthritis, cancer, multiple degenerated intervertertebral discs, various muscle diseases, metabolic disorders including thyroid diseases, diabetes, and nutritional deficiencies.

See Physician: Get an accurate diagnosis. If not a more serious problem, physical therapy may be of significant benefit.