Stomach growing, butt disappearing!

Cassandra • 26 years old. First pregnancy and I can't wait till Jan. 19th!
I noticed as my stomach finally popped out last week but butt just popped in. I had a nice butt and big hips. No change in hip size but my butt has gotten flatter. 
​Had this happened to anyone else? Can I still do my regular butt exercises as well?