confused mama

Ok. I'm 9.5 months postpartum. I breastfeed with formula supplement. I got my first period in feb very light and only a couple days as expected. 30 day cycle for march. Now I'm day 34 and 2 negative tests. Prepregnancy I was 28 day cycles. Boobs aren't sore, had food aversion and abit of nausea. Maybe stress? Haven't had a lot though. Any women had this experience?