Heartbeat in my head, what is it?

I’ve already talked about this but I want to be more specific and ask about it to maybe newer members of this app. So for a while, probably a little over a year or so I’ve gotten these little heart beating in my head episodes, especially before I go to sleep, and I’ve been sitting in my bed for a while so it must not be POTS related—but maybe some of you guys have had this. No headache with it, it is in the back of my head in the like occipital region kind of near my neck and it feels like my heart beat but a little random and irregular. It is quite noticeable and disrupts me trying to sleep which is why I am on here. I need to know what it is!! If I do something like move my head or put my hand on the spot, it will stop. I feel crazy, and maybe it’s due to dehydration or a nerve misfiring (mine often do, I get a lot of random itchiness and pain from my nerves often) but its so annoying and happens mostly before I go to sleep, I’ll notice it throughout the day in small episodes but before bed is when it may really get going and right now it’s freaking me out. Like is my heart okay?? I have 75 bpm on my watch rn so it’s not tachycardia or maybe even related to my heart. Is it my veins? I have a gene that is considered vascular eds causing but it was labeled as unknown significance and my geneticist at childrens hospital didn’t even discuss what any of that meant or if they’d test my other family members—they diagnosed me with HSD instead of EDS even after I got my two variants that could cause EDS so I am really annoyed with that (I’m 17!). I’m also mostly annoyed with my head right now so I’m ranting. Anyways, anyone else with this experience or is it just me?? I also have anxiety but I’m not feeling that anxiety in my gut (which is where I feel it primarily when I am anxious) and I am on prozac after all. Is it a medication? I don’t have a clue but it seriously is making me so angry.