If you want him to have breastmilk, work on getting your supply up. Remember that while you are at work, you will pump what he will eat the next day, so pumping a freezer full right now probably isn't necessary. Putting baby to breast is the best way to build up his supply.
Dairy intolerance is a big deal, and you may struggle with it later, so if you can, try and cut out all the dairy. I found this about eliminating dairy and how long it takes before the effects are noticed: "Eliminating a food for less than 2-3 weeks may not be effective—cow’s milk protein, for example, can persist in mom’s body for 1½ - 2 weeks, and it may be another 1½ - 2 weeks before the protein is out of baby's system." The milk you already have can be saved until you know for sure this is the problem (keep it separate so you know which the "dairy" milk is vs. the non-dairy).
Baby’s symptoms will usually begin to improve within 5-7 days of eliminating a problem food. Your baby may not improve immediately, however, especially if the reaction is to a food that has been a regular part of mom's diet. Some babies seem to feel worse for about a week before symptoms begin to improve. Sometimes it takes several weeks to see an improvement.
I don't think it will be best to switch baby completely to formula while trying to get the breastmilk cleared of dairy. I think one week isn't enough to evaluate results, though, seeing how long it takes for your milk to be completely free of dairy. Perhaps you should discuss with your doctor what you have found about dairy, and say that one week isn't enough to properly evaluate the situation and that you are not willing to completely switch to formula. Breast milk is still best, even if you have to take all the milk proteins out of it, so why would switching to something that is inferior be better? Better to give it the time it deserves and reevaluate - especially since you have not even seen signs of a food allergy!!!!! If he was in pain after eating, it might be a different story. But as he was showing YOU no signs and the doctor just found traces, I'd say ask for a new appt to reeavaluate (explaining your reasoning and research you've done to that effect) in two-three weeks and continue to only supplement when you NEED to. This is a great source for reading up on the dairy issue in breastmilk: http://www.kellymom.com/babyconcerns/food-sensitivity.html
The decision to give formula instead of breastmilk is sensitive, and one for each individual woman to make. But if you WANT your son to have breastmilk, then by all means, cut out the dairy and work on getting your supply up by nursing him as much as possible, pumping when he's not nursing, eating oatmeal (no milk, though!) and drinking lots of water. Only supplement when absolutely necessary if you want a good milk supply. My son had absolutely nothing but breastmilk for 7 full months as I worked (pumping at work), and barely ate solids from 7-10 months. So basically, he had almost only breastmilk for the first 10 months of his life, and I never once supplemented. I had trouble pumping, but made sure and had him to the breast every time he asked to eat. It's possible to return to work and not have to use formula at all, if you want.
**ETA - I think it is wonderful that someone suggested donating your breastmilk (in the freezer) if diary is an issue, BUT do read up on what is ok for donation. You can not be on any medication or herbal supplements (though there are exceptions). Here is a FAQ about donating milk from the Mother's Milk Bank of Austin (the rules are pretty similar elsewhere). http://www.mmbaustin.org/scripts/index.php?option=com_con...
Good luck!