What Causes Skipped Heart Beats?

I swim and surf regularly. 4-6 days/week. About 1 mile swimming and 1-2 hrs surfing. I am 57 yrs old, 6 , 195lbs. Had to travel for a week and when I returned I swam a mile but during my swim I felt what felt like heart beat skips. It wasn t too bad so I continued. I swam again the next day, it happened again only stronger more consistent. I didn t feel so well so came home rested. Then I went to wash the car, same thing when I exerted myself. Thought I was dehydrated so I drank a ton of water over the afternoon and evening. Next morning went surfing again with the heart skips. Had to get out after an hour. So I came home did a test, ran up and down the stairs and sure enough my heart was skipping after I stopped. Also made me not feel well. It always stops when my heart rate slows back down. So I went to an Urgent Care, explained the story, I did a mini stress test, since I told them only occurred when my heart rate was over about 120. I got hooked up to and EKG jogged in place. Sure enough about 130 bpm a big thup and I laid down and it continued as I pointed out verbally every time I felt my heart stop and start. The doctor wasn t present during the EKG. When the doctor returns he hands me my copy of the EKG and says normal. I don t see any problems. Go see a cardiologist. I have stage 3 CKD, hypertension, under control and high cholesterol but on a statin. I take Cozaar for the hypertension and CKD and eat well, low protein fish diet. Resting heart rate 55-65. The kicker is I have suffered from anxiety in the past but it s mostly under control but this new symptom isn t helping. Can t get into the cardiologist for a couple of weeks due to HMO. Afraid to exercise or do anything strenuous for that matter. Ever heard of this?