The way you are representing your sign and symptoms,it looks like you might have A.S(Ankylosing Spondilitis ) but not sure without doing any clinical test or blood test(HLB-27).
Few more details we want,like
1.do you have any stiffness in the morning when you wake up.
2.do you have any pain in your tell bone.
3.do you have mild fever in the morning.
4.do you fell hungry or not(appetites).
5.do you feel your muscles are very tight.
Next Steps
don't do any experiment otherwise it may aggravate the situation.
consult with a physiotherapist near by to you.
Health Tips
take a lot of water (3litter).