I understand mate. I think it will be worth it, as the derm might be able to give you some good advice by just looking at your hair. I've never had a scalp biopsy and the derms and hair transplant surgeon I saw were able to give me solid comfort just by examining my hair and looking through a dermatoscope. What I have noticed is that, none of them will say, "you do not have male pattern baldness", particularly if you are convinced you are thinning - they just won't leave themselves open like that, as obviously male pattern baldness can kick in at any point. However, what they all told me was that I had excellent density and should my hair deteriorate, they can help me maintain it. As mentioned, this was years ago and my hair never changed. They also take account of your family history and explain the most likely outcome, which I suspect you already know, but it is good to hear from a medical professional.
What I found most useful was that all of them said harsh lighting, wet hair, greasy hair, hair with product in etc can make hair look like it is thinning when it is not - they also showed me how photos distort the truth, especially on phones, by taking a photo of their own hair and showing me how it presented while I was sitting there looking at their full head of hair with my own eyes. So much of the advice on here like lighting shows the truth reality is simply not correct.