Health anxiety is very common and I'm sorry you have it. I always think it is wisest to have a full physical (everyone should have one annually any way). Then go from there. After a death, this can be a likely time that we start thinking about our own mortality and when we hyper focus on something like a twitch, pain, etc ,it amplifies. But seeing a doctor first lets you be sure it is not something medical going on as no one here could tell you it is and isn't if you haven't had a medical opinion first. Once you know it isn't, then you work on anxiety as if it is a cancer, heart issue, digestive issue. Anxiety IS the illness that you need to conquer just like if you were diagnosed with something. Anxiety is treatable. Therapy helps often, lifestyle things such as exercise, meditation, good sleep and eating habits and some people do need medication to deal with anxiety. No shame in it, look around you. Chances are that if you are in a group of 4 or 5, one of you will need help with anxiety or depression. It's that common. So, see your doctor and go from there.
Why don't you follow his advice and seek therapy? This is a chronic problem for you worrying about nothing, so you might get some relief from a professional who has seen people with your problem before.