Hello, I Am 24 Years Old And I Have Been

Hello,
I am 24 years old and I have been on micronor birth control for 12 months. I was prescribed this medication because I am prone to get migraines (blurred/darken vision, heightened sensitivity to sound/light, and speech disruption) and I am a smoker. From the very beginning that I started this pill my period became irregular (uncommon for me). I have been getting my period twice a month, sometimes every other week. My “scheduled” period will last 5-7 days but my irregular periods will be short (2-3 days) and very heavy. I have noticed that my "irregular" period seems to come 1-2 days after sex, after I have exercised or when I am very stressed. Is this a normal side effect of Micronor? Should I switch pills? Should I be concerned that there is something wrong with my cervix or uterus?