I get headaches at random times, did when pregnant too. Mine are either one of two things: 1. Dehydration
Or
2 my neck is out.

I try and drink more water and get to my Chiro asap. With the shooting pain on side of tummy I also had this. Rang ob. He suggested it was most likely round ligament pain or growing pains. He said to take some panadol, rest and see if they went away. If they didn't I had to ring him back and he'd organise for me to come in.

HTH