I am a 21 year old college student in my senior year at a fairly prestigious university. I am an active competitor in speech and debate and have always been very conscious of my ability to speak well. Over the past two years, I have been noticing a number of strange phenomenon.

First, I seem to to be having increasing difficulty finding words when I'm speaking where it takes me literally minutes to find easy words, or sometimes I will say something I wasn't thinking at all. Things that didn't happen in high school or my first year of college.
Second, I've been getting more headaches, which my doctor thinks is migraines, but I have still have difficulty with them even after taking medication to prevent and medication when they occur. i've been getting headaches since high school that used to typically last 2 to 3 weeks, now they are usually just one week.
Third, during the past year and a half I've had four fainting episodes, which had never occurred before, and didn't take place in situations where I was dehydrated or had any clear triggers.
Fourth, I've been getting increasingly large number of brownouts every time I stand up (from sitting or lying down), walk up stairs, it occurs almost every time to varying degrees.
Fifth, and likely unrelated, but I'll mention it anyway, I've had a horrible itch on my legs and sometimes other parts of my body. I've tried over-the-counter creams but nothing seems to work, my legs are covered in scabs from where i have literally itched the skin away. This has been going on for about a year and a half.

I've tried to talk to my doctor about some of these symptoms, except the first and third because i feel like he will say the first is just in my head, and the third i didn't really see as an issue until a recent occurrence.

Any thoughts you have would be incredibly helpful, thanks.