Feedback on site structure

There is nothing wrong with the structure you have in mind. It also allows for subcategories should that be required going forward. 

You will, however, need to think about the mydomain.com/articles page. I would assume you're going to show a list of articles available somehow. 

This type of structure allows for the use of breadcrumbs which is good for the user and also provides a good internal link structure, i.e. the home page getting the most links then the articles page then the articles themselves. To me that is exactly how it should be done.

The other links you mention i.e. about faq, etc should be footer links so within the boilerplate area. I would also include a privacy statement page. This helps in creditability. 

Let me add this small bit of advice. 

On your about page you need to heavily include content concerning your "Credentials, Degrees".  You may even want to dedicate a page for this.

YMYL sites need to have a lot of authority and you need to post your medical credentials.  Otherwise Google will not give your site due consideration.

I think the sub-category pattern for articles is a great idea. It will be easier and convenient for users to search easily for what they are looking for. Plus, as the owner, you can keep your website organized and clutter-free. Talking about "About US" page, make sure that you include information about therapies and why it's important equally. Also, your FAQs should cover all the primary concerns of clients.