VT/abnormal arrythmia

I am 43 years old, I have lived with abnormal arrthymia for a long time, over the past 12 years (since i had my last son, he is 12), they have gotten worse, about 3 months ago i went to a heart doctor and i wore a monitor for 2 weeks, while wearing it , i got a call from the nurse telling me that they picked up something on the monitor and wanted me to come in, i asked her what was it and what time did it occur, she told me it was VT and the exact time this occured was the exact time that my alarm clock went off, i asked if being startled from the clock would cause it, she said NO but I asked the DR and he said being startled could cause it, but i do not understand if that is what caused it, and if so, then should i still be worried? he gave me Toprol ER which i did take but after a few months i started having major dizzy spells,I had time where it happened while just sitting, some while standing but the strangest was while laying down at night, if i was laying on my right side i was fine, when i turn on my left side instant dizziness! never had that happen before.....so i called the DR and he changed the medicine to  Diltiazem ER, I took 1 and felt totally horrible, still light headed and for some reason, spent the evening crying (which i never do)... could being startled be the cause of the VT ?? after wearing the monitor for 2 weeks that was the only time it picked the VT up.. i did just recently go back to the doctor for a checkup (august 16th) ,i asked him again about the alarm clock and the VT, he said NO that it would NOT cause this to occur, we talked about the medicine and he said (when i called) he really felt it could not be the medicine causing the dizziness, not like what i was experiencing, he said  he felt it had to be something with my  ears..i told him i wanted to try and take half of the Toprol  , which I had already been doing at times, but now i am talking a half every day, so far i have not had this same thing occur ,but time will telll. just looking for opinions on the VT situation. thanks!