Incredibly tired

I felt so tired the last couple of days, it was the sort of tiredness which seeping through your body to every inch of your bone. My body was tensed and my neck was stiffed and it can't get any better even after I had a hot bath... yes, I caught cold, it might contribute to this and I got headache as well. I went to bed earlier every night for last couple of days lying there thinking 'how come? I used to be the person who walks 6 hours no-stop in a national park afterwards still got the energy to go swimming at the end of day... ' Having baby definitely takes its toll now... or simply just because of the age... with my back so aching, I am feeling like leaping forward into mid age...