Hello Mr. Williamson,
The symptoms that you have described suggest that you had an episode of low blood pressure, which led to palpitations and dizziness
. You have also also mentioned that you take terazosin
10 mg qid for urinary problems. The dose you have mentioned is far more than what is required and safe for you. I hope you are aware that terazosin lowers blood pressure and is also used to treat hypertension
. Please consult your doctor and discuss what happened with him. I think you'll do very well with a change in prescription and there is nothing seriously wrong with you. Please also remember that standing for hours in hot weather also increases the risk of developing low blood pressure.
Hope this has been of help. Best wishes.