Child Has Swollen And Bleeding Gums, Large Sores On Tongue, Constipation, Pain During Bowel Movement. Reason?

my sons gums have been bleeding like crazy and are so swollen they almost cover his top front 4 teeth, i have a doc appt. tomorrow morning, but i was wondering if any of you had an idea. he is eating very little, very constipated, normal amount of wet diapers, fighting sleep and along with the bleeding gums , has large sores on his tongue and his gums really really start to bleed when he strains , like when he is passing a bm or crying. he also has three little pimple type sores on his chin . he does not have any sores or marks on either his hands or his feet.