What causes cramps and spotting after heavy exercise? i'm midway through my cycle and shouldn't start my period for another 2 weeks.

Muscle stimulation: Although the uterus is a smooth involuntary control muscle, heavy striated voluntary muscle activity like exercise can stimulate the uterus to contract(cramps) as well as the small & large intestine.

Your hormones are in: .. flux for some reason. Irregular periods and spotting could mean you may have some hormonal imbalance that could be affected by many different factors, including age (if approaching menopause?), nutrition, illness, exercise (or lack of it), body girth, psychological well-being, stress, season, or simple fluctuations of other related hormones (thyroid for example). Be patient and see if it cont