Pregnancy and Posture- early changes upper back exercise

I noticed almost immediately (about 6 weeks) my posture was changing, my breast became sore and enlarged. This was pulling my shoulders and neck forward. I started to double up on my upper back exercises and stretch my chest muscles 3x/day. This was one of the few times I have ever done a static stretch before doing a strength exercise, but note it is for the opposing muscle group to enhance the result of my upper back exercise. Currently I put upper back exercises right into a pregnant clients warm up.