Who can help me with a dandruff problem?

I have really bad dandruff since I was about 3. I 've taken pills, liquid medicine, head and shoulders, selsum blue, sulfur 8, nizoral, basically any and all dandruff shampoos I could find nothing is really working. I cant wash my hair daily because I'm african american and it's not good for my hair so I wash it once a week and by the third day im flaking and itching with crazy buildup. It's so bad by the end of the week its just falling out of my hair. I'm so tired of it and was wondering if anyone had a remedy of some sort. I've tried vinegar and olive oil. Today I did mayo and eggs which made my scalp feel better and cleaned it 4 a while but im worried it wont last long. any suggestions??