I have high blood pressure and I take medicine for it but took my pressure today and it was140/102. Is this pretty serious....

Its too high. Desired BP is 130/80 or less. If the BP is higher on occasion its not a big deal but if it is higher consistantly then your medication needs to be increased or an additional medication is needed.
Yes. Go to er if you have worsening headache, chest pain, or shortness of breath. Check blood pressure 2-3 times a day and keep a log until you can contact your doctor. You may need adjustment of medications.