Pregnancy affects women differently..and every pregnancy is different. When I was pregnant with my first, I was always exhausted. With this pregnancy, I've had much more energy. It's normal, don't worry. :)
At 13 weeks I was still riding my Kawasaki ninja. Even now i still ride my bike & I feel amazing. A body in motion stays in motion. A body at rest stays in rest. You may feel exhausted but you got it in you Hun. You're pregnant. Not disabled. Try something like.... Yoga. Or... Pregnant friendly Zumba. Or... Walk at the park with pets or... Just something. and you'll get used to it and you'll have more energy :)
I am also 13wks 2days. And I've been getting more headaches and being tired. I'm sure it will pass soon.
is this your first child?