7 yo son urinating too frequently and doesn't relieve much at a time with low pressure, possible problems?

UTI or stenosis?: If this is new onset, evaluate for infection or possible meatal stenosis causing obstruction and distention of the bladder. Food dyes or chemicals can cause irritation and urgency. Some children do have spastic bladders and are never able to hold large quantities of urine before having an urge. Sometimes anxiety or stress can cause the "so scared I peed my pants" phenomenon. Start with UA/exam.