What Causes Abnormally Late Occurrence Of Menses?

last month, my period was weird for 3 days i spotted then it came but it wasnt like how it normally is. I am 7 days late this month and i have terrible gas



I am 28. 1.67 and 80kg's. My son is 7years old. I have not been on any contraceptives but i do suffer from reflux and take pills for that