Sitting is one of the worst things for you back yo do all day. You probably have tight hamstrings and hip flexors and a weak core. For now, take a hot shower or bath for some moist heat for about 15 - 20 minutes. No heating pad. Try to do some gentle hamstring stretches and knee to chest lying on your back. You can find some other gentle stretches on google. Then ice for 15- 20. See a doc. Ice a few times a day.
This post was edited on 7/17 at 9:53 am