Have you seen an M.D. or had any tests done?
Do you mean pain or soreness? Is it sharp or is it dull? Does it go away as the season goes on?
Soreness at the beginning of the season is normal. Pain that persists (or gets worse) over the course of the season is not.
I am not certain about this, and am not an M.D., but I suspect that bicep pain may be related to a flaw in your motion that is putting too much strain on your shoulder (into which the biceps muscle inserts). In particular, I suspect that it may be related to turning your shoulders before your arm is up and in the High Cocked position.
You might want to consider trying to delay slightly when you start to turn your shoulders. You might also want to consider have your elbow extended 135 degrees (leaning back toward 2B) rather than extended the more typical 90 degrees (pitching-side forearm vertical).