I had 4kids in 5years. No period in 4years. Why do I gush blood when I pee but only spot on a pad or tampon? Should I get an ultrasound?

Yes get tested. It seems like you are urinating blood without pain.Please see a doctor who will have you get the appropriate imaging study (CT-IVP of abdomen and pelvis) and take care of your problem or refer you to a urologist. It is possible s/he will start with kidney ultrasound first since it is les invasive. Best wishes to you.