is it normal to miss a period ?????

hi mwe haven't started trying again so I'm not pregnant only lost my twin pregnancy in January I've had my period three time and now nothing mine comes at 23 days and lasts four days I'm not four days late and not sure if my body is just stressed or I'm over doing it with the exercising I'm doing I'm hoping it turns up soon as we want to start trying I did have cramps the night before it was meant to come and the day I should of had it but nothing