I had breathing problem ddimer test showed abnormally high did a ct angio pulmonary result showed no clot what could be the reason could it be allery?

Many reasons : Elevated d-dimmer is non-specific and can be falsely elevated (false positive test). Its a screening test done to rule out a blood clot (pulmonary embolism & deep vein thrombosis) in patients with low or moderate probability for a clot, so if its not elevated no further tests are needed. Many things can cause false elevation - inflammation, trauma, liver disease, recent surgery and even cancer.