Nothing like a dental infection and a hospital stay to make anyone miserable. The fear of what might be can be consuming and can suck the joy right out of life.
My dear niece had 10 positive nodes and is alive today 14 years on from her treatment. Her pathology was similar to yours.
The beauty with neo adjunctive chemo with a her2+ cancer is you get to have 2 targeted therapies. Something you are not offered with post surgery treatment. So most definitely the decision to start with chemo is a good one.
By week 3 you will start to feel better and the next round of chemo you'll have a white cell booster injection so hopefully it will be a much less traumatic run.
Try to get out the house.
Have lunch out or a cuppa with a friend. Go for a walk if you can. And yes set yourself some mini goals each day...something simple so you can reflect on that achievement each day.
Keep checking in here....there's always someone on line.