Since Last Week I Have Been Having Slight Dizziness. Have

Since last week I have been having slight dizziness. Have never had before. Had a flu vaccine last Thursday a.m. and had dizziness around 4 pm. Could not walk in a straight line. Lasted for about 2 hours. No other symptoms. Yesterday had slight dizziness for about an hour. Could walk, talk and function but felt like I was walking on a boat and head felt as if it was constantly moving. Today, same as yesterday. No fever, headache, sickness of any other kind. Had school nurse check and blood pressure was good. Am in good health and never have anything wrong. Just regular annual checkups, etc. Have good blood pressure, cholesterol, etc. readings. Only meds I take are vitamins, generic version of synthroid. Exercise 3-4 times/week. Thanks. email YYYY@YYYY