Overthinking physical or mental symptoms to the point that in itself causes you a problem is likely "health anxiety". It is really common and happens to a lot of people, especially when they get sensations related to chest pain, breathing or headaches because those with health anxiety will usually disregard occams razor and jump straight to chest pain = heart attack or dizziness = brain tumour.
There isn't too much that can be done for it other than to practice some mindfulness techniques when you get anxious about these things, you might be able to try a beta-blocker like propranolol if you get a lot of physical anxiety symptoms (palpitations, hyperventilating, shaking, sweating etc.) that then exacerbate health anxiety.