Could we not guess and only provide answers we actually know?
It's hormones. Hormones make you super horny but it can also make you have a low sex drive. They fluctuate, up and down. This isn't a problem and only would be one if this went on years down the road.
Even when you get older this happens. Nothing to worry about. Some days it will be higher than normal and other times it will be low. Just how our bodies work.