Hello,
This could be post viral weakness.
The pain you described also suggest sciatica.
But needs physical examination.
The stomach may be rigid due to hyperacidity, probably sometimes you must be feeling constipated as well.
Next Steps
Take medications that will relieve you from hyperacidity.
Have plenty of fluids to rid of weakness.
Health Tips
Avoid oily food.
Avoid extra spicy food.
Have fibrous diet.
Have fruits.