I am guessing this is just a thing that happens when you play to much. Besides taking a break, is there anything I can do? like stretches or something?
There are a few places in your arm/shoulder that can get sore. Remedying the problem relies on identifying where exactly it is. What part(s) of your arm are complaining? Wrist? Elbow? Triceps? Shoulder?
Some of these are definitely a little awkward at first, but making them habitual may help you out: