Period almost a week late! Why???

Meli

The last time I had unprotected sex (was on the pill just no condom) was in May and haven’t had any sex since. I have had my period since then but it was always 2-3 days late. My diet has also been not the best I typically eat a lot of fast food, rarely any fruits or veggies. I’ve been on and off stressed about school and work but I don’t think I’m stressed THAT much. What else could be the reason???