Me and my husband are trying for a baby for the past one year. My periods were regular but for the past two months I could find spotting on my 28th day and then regular period starts after 31st day. Will there be any problem in my ovulation? How do I calculate my fertile days.

This link will tell you how to calculate when your ovulation is.
Using Basal Body Temperature Charting to pinpoint Ovulation (http://www.babyhopes.com/articles/basal-body-temperature-charting.html)