Breastfeeding While Pregnant

A little stressed out and in a dilemma. Is it true that BF while pregnant can cause a miscarriage? My first LO just turned 1 and I’m expecting my second. I’m only in my first tri. Awfully sleepy. I decided to start formula because my nips feels tender and sore but LO is having a hard time transitioning. She’s been fully breastfed up till a few days ago. How do I go about this journey? It hurts to see her cry for comfort especially during her night wakes and morning naps. She refused the bottle even on other feeding times… help..