Dear friend. Thanks for sharing your concern. Yellow pigments on your teeth could be hard deposits like calculus,which does not get easily removed upon regular brushing. Also your history suggests that you have multiple decayed teeth,that is due to improper oral hygiene. Thus teeth has become,brittle and extensively decayed thus getting fractured easily. I would like to advise you please visit your dentist and get your teeth cleand (scaling) and also take x rays to see how many teeth are cariously involved,and the extent of their decay. Further on various appointment, all teeth can be restored suitably. This should solve your dental problem. Hope it helps. Thanks. Take care.