Regular but long periods.

Autumn • TTC with my first. ❤ in love with my boyfriend.
My periods are pretty regular since I've been off of Depo. They're usually about 29 days apart but they're long...I've been on this period since June 1st and I'm about to get off it, I can tell because the flow is lighter. But why are they so long? They last around 9 or 10 days. Will this affect ovulation and getting pregnant/TTC?