Heredity thinning or diet problem?

[Stephere]

I'm 21 years old and my hair has been falling madly for the past 3 months (hairline is receding too). Visited a dermatologist yesterday and was told that I was suffering from heredity thinning (phase 3?). He prescribed me a Minoxidil 5% to use twice a day.
Anyway, it bothered me that he did not look at my scalp much, when I said I had dandruff (I would find some hard nits too), extremely oily scalp, and not to mention that I was on a diet 4 months ago(had only sweet potatoes for lunch for about 1.5 months). He brushed them off with the reason that oily scalp and dandruff do not cause hair loss. And the visit yesterday cost me a whooping $250. I can't afford going to another Doctor now.

Which of the reasons above could my hair loss be due to? Should I continue using Minoxidil?

Also, I am going to shave my head next week. Should I do it?

 

[GoldenMane]

If your hairline is receding and you're thinning in a male pattern baldness pattern (top only, back and sides intact) then it's definitely male pattern baldness. Oily scalp and drandruff are a common symptom of male pattern baldness but not the cause.

 

[Stephere]

If your hairline is receding and you're thinning in a male pattern baldness pattern (top only, back and sides intact) then it's definitely male pattern baldness. Oily scalp and drandruff are a common symptom of male pattern baldness but not the cause.

My hair at the back is thinning a little as well, I can see the scalp on some areas at the back. 1-2 strands of hair come out whenever I run my fingers through my hair gently (the back included), which was never the case before. What should I do?