Hello and Welocme to HCM, I am Dr Mbong. In some women, strainous physical activity is associated with irregular periods, and given the fact that you are physically active, this may be the reaosn for the late period. If it persists you will need to see a physician for thorough check-up in search of other non-pregnancy causes may be related to late periods. As for your diarrhoea, since you have not changed your diet and do not have a known enzyme deficiency (like lactose), you may have picked up a bug unknowingly while eating which presents with more subtle symptoms that those that cause acute food poisoning especially if you have been traveling lately. Giardiasis, a sort of intestinal ameba bug can do this. The diarhoea can also be due to some bugs u may picked up if you give your partner oral sex of the vaginal and perineal areas, which contain lots of germs which can cause diarrhoea such as salmonella, campylobacter, escherichia. The best way to know which germ it is and the appropriate medication to take, please visit a clinic and please do a stool. I wish you quick recovery.