What is wrong with me?

hi, for the past week i have been feeling really sick in the mornings but not actually been sick and i have also been getting cramps in my stomach and womb, im not actually sure when my period is due because i have really irregular periods so therefore i can't tell if i have missed one, the last time i had sex i did use a condom so im sure im not pregnant has anyone else got any ideas what else could be causing this.