Thawed breastmilk

I go back to work next week and have been working on my freezer stash. The last time I reheated breastmilk from the freezer, it was oddly chunky like sour milk. Not the normal separated way where the fat is on top but once it's warmed it all meshes back together. This was like chunky pieces floating in the warmed milk. Has this happened to anyone else? I'm afraid my milk won't reheat from the freezer correctly and my husband will end up not having enough to give our daughter. Any thoughts?