You should see (or at least call) your doctor - this doesn't sound normal to me, in particular if you didn't have these headaches prior to pregnancy. I got those migraine headaches towards the end of my first pregnancy and ended up being induced due to pre-eclampsia, so you should get your BP checked. The headaches are just one of the symptoms: http://www.preeclampsia.org/symptoms.asp
And, while preeclampsia is more common during first pregnancies, since it's been so long since your first, your body is likely to react more like a first pregnancy.
Another possibility is that you are low in Magnesium = it helps muscles relax, including those in head/neck/jaw. I used to have debilitating migraines and since adding magnesium (and switching to a GF diet) I have had a single one. You cannot really take too much magnesium as you will excrete excess and this would be far safer for your baby than taking any pain relievers daily.
Also, do you use artificial sweeteners. Those can cause headaches in some folks.