Sound like you need to really up your water intake. That could be what's causing the headache.
I've been dehydrated before & had a bad headache at the same time. Sounds pretty normal, I'm sure the er checked your blood pressure. If you continue to feel this way get checked out w/ your obgyn. Tylenol is pretty much all we're allowed for pain.
I have very intense headaches when I'm pregnant this time and last almost everyday it's actually more common than you would think could be blood pressure or dehydration or in my case just changing hormones. If it continues to be a problem talk to your doc, they'll check your blood pressure and stuff. Just do your best to stay hydrated and you can take tylenol for the headaches. Good luck!
Could be low blood pressure, low blood sugar, you could have been dehydrated. The baby will make you dizzy because your body has to pump blood through your body and to the baby. Tylenol is safe to take (unless your doctor told you otherwise) to help with the headache.