Hi Trisha,
That happened to me occansionally. I found that if I kept pumping for several minutes after I "ran out", i'd get a second letdown that was mostly the fatty hindmilk - this usually added another 2-3 ounces to the harvest and occured at about the 21 or 22 minute mark during pumping. When I swirled the milk after it separated, the bluish foremilk became creamy again.
My son also went on strike at daycare - would refuse all bottles all day and then nurse me dry as soon as walked through the door. We switched to the Gerber Nuk nipples - that helped - and I also gave him a bottle of breastmilk occansionally starting about 6 months. I'd tuck the nipple down near my breast and that seemed ok with him. Before that, I was afraid he'd decide that he liked the bottle better and refuse to nurse, but no way - he knew a good thing when he had it.
Good luck! I hope this helps.