You might want to see a dermatologist about it since they can help you a lot. However, I went probing around the internet and I read about this one person who suffered from severe dandruff and used a product called Nizoral. It might be the same thing as Ketoconazole - but it doesn't hurt to try another product
However, I do recommend that you see a dermatologist - they can help you with skin problems. Do you have oily hair? Maybe that's why you get the pimple-like bumps on your scalp?