Need to lose weight...

So, I planned on trying to lose some weight before conceiving, however, we were blessed enough to conceive before I could lose any weight.

What are the restrictions as far as exercise during pregnancy? This is my first time being pregnant and I am scared of messing something up.

Can I do normal workout programs that I’ve done in the past? Does it need to be modified this soon in the pregnancy? Should I stick to walking and yoga?

Just trying to find out how much is too much.

Thanks!!