Breastfeeding and Periods

So, we were staying to wean before quarantine started, but being home with my child all the time has eliminated that and now he's nursing to sleep every day. I was in the pill up until mid March because I'd had several weeks of breakthrough bleeding. They told me to take a week off and then restart, but we decided to just stop for a while. I had what appeared to be a normal period at the very start of April, but have not had one since. After experiencing some symptoms for a few days, I started taking pregnancy tests every week, but they've all been negative. Has anyone else experienced something like this? Could symptoms be related to stopping the pill? I know it's not likely that the lack of period would still be from breastfeeding, but I'm stumped.