do you massage the MTG into to scalp in the crown area?
what about vatika oil? i've read people rave over how it helped fill in thin areas. maybe massaging it into the scalp will help.
also, maybe taking vitamins (biotin, sea kelp, msm, b-complex, flaxseed... etc) might help.
i know for me, when i let myself get stressed out, that it takes its toll on my hair. maybe stress could be causing it too?
also, i wanted to ask what chemicals are you putting in your hair? maybe you need to clarify your hair and scalp... maybe apple cider vinegar rinses after most washes will help sooth the scalp... maybe it could be bacterial (if so, maybe coconut oil or tea tree oil scalp massages could help).
hope this helps!! (and i hope you find and fix the cause of the soreness and thinning... i know how it feels, and it sucks hard)