9 yr. Old male - nosebleeds that have gotten frequent/lots of blood during the last month - happening multiple times a day and every night?

Nosebleeds. In a child this are, nosebleeds are usually due to trauma, often from nose picking. The dry air in air conditioned settings doesn't help either. A small amount of either vasaline or antibiotic ointment, applied gently to the inside of the nose, will help keep the lining moist, which will help prevent nosebleeds.
Other symptoms? Agree with nose picking as #1 cause. However, if the nosebleeds tend to be heavy and last >15 minutes, or the child is having any other symptoms such as bleeding gums, blood blisters in the mouth, or unexplained bruising in strange areas (back, chest, etc.) then he should be evaluated. He could have a low platelet count.