Hi thanks for asking question.
First you have to rule out is anemia
.Estimate your hemoglobin
level for it.If hemoglobin comes low then chances of weakness might be there.For that iron tablet has to be taken.Peripheral smear study also helpful.
Second possibilty is of simple musculoskeletal pain
,that might be because of heavy exercise or improper sleep bad posture.Simple analgesic
with proper sleep posture will be helpful for that.
Third this pain may be as part of viral infection or respiratory cause.Do CBC with chest x ray
Maintain healthy nutrition with more water.
Mostly with time in few days you will be alright.
If still have problem then further work up will be done according to physical examination.
I hope i have solve your query