I think you should ask your PCP for a full hormone level blood panel to rule any endocrine issues out.

Sometimes endocrine issues pop up during puberty and pre-puberty because the body's hormones are gearing up for such a huge change.

Hormone deficiencies can cause weird brain fog because your brain doesn't have enough fuel: otherwise known as glucose. The feeling becomes more apparent after a little bit of physical exertion. (Hormones help your body/brain metabolize the glucose...)

I hope this makes sense.

Hormone deficiencies can also cause headaches and tinnitus.

The blood panel is quite simple and just takes an order from the Dr. and a trip to the lab. If anything weird comes up, you will be called for additional testing.

Tell the Dr. your symptoms and ask for a full panel.