My ribs, oblique muscles, chest, and legs are sore as if i've done a full body workout when i haven't. can this be due to carry a very heavy backpack?

Muscle pains: If you experienced these pains after carrying a heavy backpack then it is reasonable to assume the pains may be a result of this. Try Tylenol to relieve the pain. Take a break from carrying heavy items. If the pains persist, then see a doctor. If the pain is concentrated in the chest and worse with exertion, associated with breathing problems or radiates to arm, then see a doctor immediately.