I'm kind of going through something similar at the moment. I am also 27/m and an athlete.
I was diagnosed with GERD/Gastritis about a month ago and I noticed heavier heartbeat and occasional pvcs with the same double beat and skip. I sometimes get about 4-5 of them and then back to a normal heavy beat when I also get up too fast to do something right away. Like you, it freaks me out so I just had some bloodwork and an Eco done this morning. They also gave me a Holter to wear for the day. I also go through the worst case scenario thought process and think "Uh Oh! I'm having heart failure!"
The lady doing my Eco kind of freaked me out for a second because in the middle of it she said "Hold on for a second, I will be right back" and brought in the guy who does the Eco readings to take a peak at the Eco while she was doing it and said to him "look right here". There was a pause and I started panicking because you think there's something wrong when this happens and then the guys goes "it looks good". Then he asked me "are you an athlete?" and I said "yes" and then he said again "ok, it looks good" and walked out. Then she was like "well I knew he was right down the hall so I figured I would ask him while he was standing right here". I am thinking he was seeing what my primary care doctor saw the other day which was a couple extra beats which I was told was normal for athletes, but it scares you none the less.
I think alot of my heart related issues are also due to anxiety. Get some testing done to ease your mind if need be.
If you are truly scared, schedule an appointment with your primary and tell them what's upsetting you.