Suggest Remedy For Sharp Headaches

When do you know do go to the ER for high blood pressure? I am not diagnosed with high blood pressure but the last few weeks have experienced it. My lower number has been in the 90's mostly. My Dr. thinks its from Cymbalta and is taking me off it but tonight my pressure was 145/105 and I'm having sharp headache pains. When do I know when it is dangerous? Thank you! I'm a 39 year old female, 5'5, 153lbs. non-smoker.