Issue on recent events which is occuring

I have been experiencing episodes of lightheadedness/subjective unsteadiness, sometimes feeling as if I may be pulled backward, without actually falling or losing my ability to walk. I also sometimes get very brief headaches and a vague visual sensation, and reading text line-by-line on my phone can aggravate a nausea-like feeling and sometimes increase my heart rate. I experienced similar sensations during my prelims preparation and exams, particularly around periods of fatigue/stress. Recently, I had a bike accident about 15 days ago; I don't clearly remember whether my head was involved, but I don't recall a definite head impact, had no visible head wound, no loss of consciousness or repeated vomiting, and was able to write exams and perform practicals normally afterward. I also had a separate pool accident about 5–6 years ago in which I fell backward onto the tiles, briefly lost consciousness, and had a nosebleed, but recovered within about an hour and subsequently went to an adven