Has anyone had a problem with not ovulating due to being underweight?

I have a BMI of 18 and have lost a bit of weight recently and not on purpose

I have been testing for ovulation for a few days now as I have not had a period since my d&c on oct 7th. Am I totally testing at the wrong time ? Or could my weight have something to do with it? I'm reading a conception book and it suggest that.... Just wondering if anyone has had a problem in real life with this?

Or when would be the best time to test for o?