Around two of Twixes nipples there are swollen lumpy things. The nipples themselves aren't swollen or pink, but she hasn't been spayed (I'm going to let her have one litter of kittens before I do), so I don't know if the lumps are from milk if she's pregnant. They are approximately 1/2 a centimeter high, but you can definitely tell that they are there. Is this anything normal, or should I get them vet-checked?