I have just googled and come up with this, Early Pregnancy. Headaches are very common in early pregnancy, and are most often caused by pregnancy hormones and the dilation of veins in the brain. Sometimes they're also due to stress, tiredness or dehydration, so drink plenty of water and grab a rest whenever you can.
Later pregnancy
Later on, headaches can be associated with high blood pressure, as you mentioned, so it's important to get it checked regularly and mention any headaches to your midwife.
Your eyes change in pregnancy, too. So if it's been a while since you had your vision tested, make an appointment with the optician. If taking two paracetamol doesn't cure a headache, speak to your GP or midwife.
I hope this helps hun xxx