Who got pregnant while breastfeeding ?

Moms who got pregnant while breastfeeding and were not using any form of birth control what were your symptoms and how long did it take. I am not trying for another baby but we are not preventing either. I’ve been extremely tired I feel nauseous, have times when I’m dizzy. Was thinking pregnancy could be to blame. I have not had a postpartum cycle yet, and my daughter is 3 months. She isn’t exclusively breastfed. She is also formula fed. Experiences please!