More than likely its something that you've eaten that's upsetting the babies tummy
How old is she? It sounds like a possible couple things (not your milk going bad) but need more information before I can say...
She is a month old in a few days.
Could be reflux. Which is a reason for the agitation, look up a messy eater and there are ways to try ans help. it could also be a lactose intolerance. You can try cutting dairy for 2 weeks and see if it helps...specially if you notice blood specs in her stool.i would s also bring it up to you pediatrician and let her or him know what you are trying to do to help rule out things.