You begin with many follicles ( regardless if you are fertility
meds or not) each containing an egg and competing for dominating position and hormones. Around cycle day 8, one becomes the dominating follicular and will be the one that ovulates. Most of the other follicular have dies or are too small in size to have a chance to ovulate. These remaining small follicular stay around to support the dominating follicle by producing hormones for it and the lining.
This is the nature' s way and nobody can predict on which side of ovary,you are going to ovulate.
It is perfectly normal to have one follicle and why it happens,no body knows.