you may be hearing the pulsation from a branch of your jugular vein. like an artery the jugular vein has a pulsation that you can hear at times because one of the branches is anatomically close to the middle ear. there is a condition called pulsatile tinnitus but based on what you have shared this would not likely be the cause in your case.
what causes me to hear a pulsating sound in my right ear? when i press on my neck it goes away.