Thanks for the replies, ladies! Since the sour bag, I have defrosted 2 more, and they were also both sour...

I have no idea what happened.... I will continue to defrost and see if any are good, but I am quickly losing hope. I have no idea what would've caused this... They are from different time periods (so far out of the 3 sour bags, one's from July, one from August, and one from late November), and dh and I wracked our brains trying to think of anything that could've caused the sour milk. The only thing we could think of is that we had a power outage in mid-November, however the power was only out about 2 hours, and during that time the deep freeze was not opened. Plus, that wouldn't explain the sour bag from late November... I have no idea and I'm so upset!!!

Any other ideas from anybody??? I'm desperate to know what happened....
As far as my decreasing supply goes, I will have to call LLL because after this dissapointing turn of events, I find out that my ds is allergic to milk (and it's quite a severe allergy at this time), and the pediatric allergist told us that when I'm done breastfeeding (I actually only pump and feed), we should give him soy formula until he's 2 (if he doesn't outgrow the allergy by then--which we won't even know for a year if he's outgrown it), which could get quite pricey, so I would like to be able to breast feed for as long as possible! I don't know how the whole buisness with having a toddler I would like to breast feed, and being pregnant would go.... Maybe I'll write a post.. lol
Whiskers