Hi!
The nicotine in smoke can cause vaso spasm or contraction of blood vessels. The spasm is temporary and goes away after some time. Hence, when you give up smoking, the symptoms disappear. If you are having problems with erection, then please give up smoking completely as with time the blood vessels to penis may become damaged. Also, you may need dopplar studies to look into the blood vessels of pelvis and penis. The symptoms can also be due to aneurysm of the abdominal aorta (AAA). Usually AAA and heart conditions present with other symptoms (increased heart rate, sinking sensation, sweating, etc) apart from a pulse that can be felt on the outside. This can be diagnosed and treated by a vascular specialist and an angiogram not ultrasound is done to detect it. Severe acidity, gas in stomach and muscle twitches too could be causing a pulsing. If heart and aortic causes are ruled out, then this should be looked into. Do consult your doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.