Chemical pregnancy after getting off pill

I took my last pack of birth control pills in January, so I have been off of the pill 4 months. I just had a chemical pregnancy last week. I was only around 4-5 weeks pregnant. I know people say it's fine to go ahead and start TTC again, but my only worry is that the reason I miscarried could be because the pills aren't completely out of my system. My period cycles have been super long like 45 days long. What do y'all think?