How serious are my heart palpitations?

About two years ago, I had a spontaneous supraventrictular tachycardia, about a year after my young mother suffered four consecutive heart attacks. When my parents realized that my pulse was 200 bpm they rushed me to the ER, and when nothing worked to slow it down, a shot was used (I can't remember what medicine it was). For about a year after, I was monitored and put on beta blockers, and when no symptoms persisted, my cardiologist took me off the medication. After that, everything felt fine for maybe six months. Then a few minor tachycardias began to happen every now and then but they would go away with the basic cough or cold water shot. But for about the past three months, my heart has skipped a beat at least daily. This didn't really concern me that much, but soon instead of just a skip the fluttering would last at times upwards of an hour, making me dizzy and causing black spots in my vision. These happen at spontaneous times and have no relation to what I've done during the day, including what I ate or the number of hours of sleep I've had or how stressed I am. I blacked out in a movie theater for only a couple seconds becuase of a sudden slowing of my heart, even though I had been sitting still for at least 30 minutes. The palpitations happen probably once a day, but it is rare that they last more than 15 minutes. The more severe episodes I have had though have left me with residual chest pain for the rest of the day and often the rest of the week. It feels like the palpitations are getting worse and worse, much different than my manageable tachycardias. How serious is this?