Hi Myrrh and welcome,
Yes itching is normal, next you'll get bud development, and they will feel sore/tender forever. Learn to LOVE it!
Since your on a fairly low dose of PM, I'd say to quit for awhile, and see if the itching stops, Then try 500mg a day to see what happens.
Since your new to PM your body has to try and make sense out of what the hell you are doing to it.
While your here, stop by the introduce yourself tab and tell us a little bit about you and your journey so far.
Happy growing.
Bobbi
PS you should take calcium with your PM. It has a bad habit of depleting your regular supply. about 600 mg should do the trick.