Way to go! I LOVE high school tracks - ideal place for any kind of exercises. It is easy to measure distance, ideal soft surface to protect legs, there are benches to leave water, sweat-shirt, usually there are water fountains, bathroom. Safe(r), clean(er)... The most important: outside:-)))Should I continue?
Our high school tracks are always very busy - dozens are walking, running, etc.
Feeling weak could be caused by lack of vitamins, or minerals - or many other reasons.
Calcium, magnesium, might help - usually they are sold in some kind of combination (sometimes with Zinc.) Potassium also.

I second IdahoSpud, if you started LC-ing a couple of days/weeks ago, it can be simply from your body adjusting for the new fuel:-)
Do not give up the walk, take it easy - you will see how fast your energy is back, even multiplies.