Don’t know what to do

Hey everyone. So my partner and I rescued a dog in 2021. She was about a year old when she was found on the streets in South Carolina. We adopted her 2 months after she was placed at the shelter. Upon meeting her and bringing her home, she was very scared and anxious about everything, but we figured it would take some time for her to adjust. She hadn’t shown any signs of aggression with other animals or infants. Now 3 years later she is just as anxious and scared about almost everything and becoming more reactive. She has snapped at 2 children with no real warning songs that I could see. One toddler age and one tween. She growled and snapped at a puppy today. I feel like I can’t trust her anymore. I don’t know why she has suddenly started to show this “biting” behavior. I’m now so anxious whenever she is near someone else, and my partner gets so mad at me because he says she can sense my anxiety which makes her feel worse. But I can’t help feeling so scared she’s going to actually bite and hurt someone. She’s a pitbull mix so I know she is capable of doing serious damage. And to add to it, I’m 4 months pregnant which has me terrified of how the dog will act around my newborn. It just breaks my heart, I’m at a loss. Any advice would be appreciated.