what you describe with occasional high blood pressure
pics, palpitations and abdominal pains are a classical presentation of a particular cause of hypertension
which is called, a phaechromocytoma. This is a tumour of the adrenal gland that causes excessive secretions of hormones called catecholamines involved in hypertension. I would wish that this should e excluded before any other causes be sought. Urine levels of vanyl Mandelique acid and other blood hormones are usually measured. An abdominal CT scan
is usually asked for in most cases.
Consult your cardiologist for a a proper evaluation.
Thanks and hope this helps,