I believe the condition you are describing is Feline Cystitis. There are 2 types. One with crystals and one without. I remember Jasmine addressed this issue with someone else a while back who also had a similar problem with their cat and also had a new baby. The introduction of the new baby into the house was causing an emotional stress for the cat. Usually a change in food (see your vet) and antibiotics administered by your vet as well as some separation away from the baby will aid the cat in adjusting to the new situation at home.
I hope things improve for your kitty. Please let us know how things turn out.