As I understand is, Dyscalculia affects your ability to manipulate numbers and do math. There is a lot of math involved in chemistry so this condition does sound like an impediment. However, since I don’t know the particulars of your condition (and since I’m not a psychologist) I have no way of knowing if you could over come this handicap to become a chemist. I certainly hope that you’ll able to pursue your dreams regardless of what they require!