BTS breathing can be very erratic and hard to gauge before you get used to what "normal" breathing looks like. Normal breathing can vary anywhere from a shallow breath every couple of seconds, to a deep, almost sigh-like, breath that seems to inflate the whole skink as "rarely" as every 20 seconds or more. If you are comparing to human breathing you can get freaked out real fast.
If he is eating and moving about, I would try to not worry too much. There is nothing wrong however with taking him in to a vet just to get a base-line update if he is healthy, and to get a quick start on a treatment if the vet thinks something seems to be off. So don't hesitate.
I ALWAYS suggest having a vet that you are comfortable with, who seems able and willing to treat a BTS, BEFORE there is a problem. That way you can already have discussed with the vet what you do if there's a concern or emergency in the middle of the night or on a weekend, because, far from every emergency or off-hours pet clinic will see an exotic pet.
Just some things to think about.
He also seems to be getting an awful lot of food for a 1 year old skink. I would maybe stretch out feedings to every 3-5 days with no pellets in between
He may well be feeling rather engorged. 
