What Causes Stomach Aches, Dizziness And Missed Period?

Hi, I would like to ask ... currently Im experiencing some discomfort such as stomach aches, light cramps in it, and in lower belly, also felt like fever in it, some nausea and dizziness anytime during the day, more gas and burping, food aversion, but often hunger and I got like mild mestruation cramps for 5 days at time my period supposed to come but its missing for 7 days already... any idea what its caused by?