Dear Welcome to HCM We understand your concerns I went through your details. I think you may have a medical condition called pica : this is a type of eating disorder, when a person feels a need to eat non-food substances. Different people with the condition eat different substances: some eat soil, some paper - and the list goes on. Chalk is in fact one of the commoner ones on the pica list. There are several possible reasons why you have this condition, and you definitely need to see a doctor to find out the cause and to get treatment. Some people with pica are lacking a nutrient in their diet; but it may be caused by an underlying mental health problem. Chalk (calcium carbonate) is generally considered to be non-toxic, but eating it is not advisable and it may result in the following problems: abdominal pain, nausea, vomiting, constipation, diarrhoea. The chalk from the dust may cause eye irritation, and isn t good for your lungs. Some kinds of chalk may contain toxic additives. If you require more of my help in this aspect, please use this URL. http://goo.gl/aYW2pR. Make sure that you include every minute details possible. Hope this answers your query. Available for further clarifications. Good luck. Take care.