skipped heartbeats are almost always harmless, and a misunderstanding of how the heart functions. Your heart rate is never truly steady, and it changes speed based on demand at that moment. for anxiety sufferers, this can be a problem, since we're.. you know, terrified.
One thing to watch out for is if you actively check your pulse, you become subject to the "stopped clock illusion." This is a weird phenomenon that messes with how we preceive time. If you were to look at a c lock with a ticking second hand, the first second you see after looking will appear to take longer than the seconds that follow. Measuring your heartbeat causes this too.
You can't accurately measure such things without one occurring, resulting in the skipped sensation as your brain tries to fill in the past that it never actually experienced.