Chris,
If your Dermotologist has determined that there are no signs of MPB & your hair doesn't appear to be thinning, forget about it. And I mean that literally! Don't think about it, don't tug on it, don't check your comb or your shower drain.
MPB is obvious once it begins.
Get on with your life, you ae young only once. Time will come to worry about alot of things as you age. So don't waste time, energy or money worrying now. It is a waste of precious youth!
Take it from me, I am 51 yr's old.