I missed my period for a month but it came a month after with a heavy flow what may that mean?

Possibilities: Some women occasionally miss a cycle, which may indicate they did not release an egg as expected. That would lead to an estrogen dominant buildup of uterine tissue & potential heavy menses when that was overcome in time. Cycles are usually driven by estrogen early but other hormones released by the egg follicle later that trigger the end when pregnancy does not occur.