At 30 I had 3 bouts of A-fib & it has not returned.I had test and all is ok.I now have pvc when laying down.?

The A-fib was caused from drinking ice cold liquids after getting hot. Then when I would take a hot shower I would convert back to sinus rythem. The first time I went to er and was admitted for two days. I converted back on my on when I took a hot sponge bath. They did ever test they could and said I had very healthy heart. It happened two more times in the next three months when drinking cold liquids after getting hot. Then when I would take a hot shower I would convert to sinus rythem and now almost 3 years later I haven't had it again. Now I have pvc when laying down and doing random things. Again the Dr. said no worries that lots of people have them. I just want to know what in the heck could all of a sudden cause A-fib randomly for three months and then pvc that come and go as they please.