Workout advice needed

I just found out I am about 3 weeks pregnant. I was working hard to lose weight before I found out. I know you can’t diet while pregnant but you can still workout. I’m hoping by working out that I’ll at least maintain my current weight and/or be more fit in general. My issue is that I have a bad back from breaking my neck as a teenager. What are some good exercises that won’t stress out my back too much? I’m hoping that walking is not my only option.