off bc in September and need advice on ovulation question

Juli
Hey everyone! I'm new on here and had a few questions. My husband and I are trying to conceive baby #1. I got off bc in September and just got my first period since being off bc 10 days ago. It is super light but has been going on for longer then the 5-7 days that I usually have it. My question is. How can I figure out my ovulation date when I've only had one period since getting off bc? Has this happened to anyone on bc?