Hi Noel! Did you have your MRI? An MRI without contrast is not ideal, but it can detect a lot of abnormalities, since you are breastfeeding, it is the way to go at this point. It can always be repeated in the future.
The doctors probably don't want to use dye when your breast feeding. Ask your doctor, if you pumped and saved your milk for a while, then maybe they could use the dye, and just not breast feed until it's out of your system.
I don't want to scare you, but your symptoms do point to a brain tumor. Because when I was diagnosed the doctor asked me about numbness. Now, that I've had the Gamma knife, I do have facial numbness 1/2 of my face is numb pretty much all the time and food doesn't taste the same.
Well, good luck and let us know what you find out