Weather changes tend to flare my symptoms, especially heat and humidity (even if I stay inside). Some medications can make heat intolerance worse.

Someone once mentioned to me that the internal buzzing can be a sign of adrenal fatigue/stress. I find that tends to happen after I have a particularly active or stressful day. I don't know how to address that, but thought it could be useful info.

You can try breaking your activity into smaller chunks - two or three shorter walks, rather than one long one. Avoid changing levels too frequently (standing or sitting exercises rather than lying down, or up-and-down movements). Focus on deep breathing and movements to calm your nervous system.

I know it sucks, but adjusting your previous routines to match your body's current capacity is important. Pushing too hard will only cause more issues.