Stringy/clumpy milk is often associated with mastitis, but it can also be normal, or be related to nipple trauma (e.g. from a poor latch or poor shield fit). A soy lecithin supplement, fixing your baby's latch, reducing saturated fat in your diet, and adjusting your shield fit may all help.
I think a lot of people are shocked by the occasional stringy/clumpy nature of their milk, because we're all most familiar with the pasteurized and homogenized milk we get from the store. But any dairy farmer will tell you that there is a filter on the milk tank to catch all the stringy/clumpy stuff (and also the cow hair and hay) that is normal for milk straight from the cow!
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"