I take a multi vitamin supplement and it does not affect my brain. I am better than I was before I started it. Bartonella was the culprit that gave me depression, apathy about existence and the feeling that I was just not completely there. Treating bart made a huge difference in a short time. Your symptoms could be just lyme but the emotional part seems like bart. I believe B vitamins are depleted by Bb and it is important to replace them, especially B6 and B12, a deficiency of which can cause depression on it's own. Many of the symptoms of B12 deficiency are the same as lyme. Magnesium is also depleted by Bb and it is important to supplement it in chelated form. A magnesium deficiency can cause nerve and muscle problems, like spasms and cramping. I do not follow the logic that starving the body of important nutrients you need for optimal health will starve the lyme. There are different theories about how to treat this disease and it can become very confusing.
Don't worry about starting abx. It will knock it down and you will feel a lot better after you have gone through the herxing process. This is a nasty bug, very hard to erradicate. Make sure you are addressing all the co-infections because it is a waste of time to treat lyme when you also have bartonella or babesia. I know how you feel. It is really awful, but you will recover and feel better.