There can be several explanations for this but the most logical might be to look at how you are handling milk. Human skin is notoriously covered with bacteria and if not cleaned will contaminate everything in its path.
Even washing one's hands can not prevent contamination entirely.
Here is what I would suggest.
1. Handle milk exceedingly carefully: a) wash hands before touching the top.
2. Take the top off with one hand, pour the milk into a container and replace the top without touching the inside of the top or the top of the bottle/container.
3. (now this one is obvious but only directed at a select few): don't drink from the bottle...nuff said there.
4. Look for milk that is "ultrapasturized" which will last signficantly longer in the fridge. Out here we get it in 1 quart boxes rather than opaque plastic bottles.
5. Be certain that there are no "hitchikers" on your food in the fridge. Molds, etc. seem to grow faster on some things and having that in the fridge and in the circulating air of the fridge is NOT in your best interest.
6. Clean the fridge out with a dilute bleach solution on occasion. Yes, cleaning the fridge can be very useful in solving this problem.
7. Don't leave milk out on the table, counter or let it get warm. That is a BIG no-no. It invites all kinds of critters to infest your bottle.
8. Don't let the children handle the bottle. Keeping it sterile as much as possible should extend the life of your bottle of milk quite a bit longer.
An interesting result of sour milk is that it can be used to make "sour-dough" baked goods. You can read all about that somewhere else.
HOpe this helps...even if just a little
