How did the first week of Phase 2 feel? Are you feeling energized and happy? Hopefully the answer to that second question is "yes!" That means the trainer is working, you're getting all the nutrients you need, and you're learning how to manage your time.
If you're feeling really run-down and tired, then it may be in your best interest to take another day of rest after this one. If you're feeling bad, you may also want to look at your nutrition. Are you eating enough? Are you getting lots of nutritious food? Breastfeeding and exercising means your body needs a lot of calories. So eat up!