I went for a Doppler Ultrasound but the injection they gave me Didn't cause me to have an erection is that a bad sign?

Injection? Definity? What injection did they give you during the ultrasound? Was it a contrast injection of agitated saline or Definity? I'm not sure who / why you expected to have an erection, but that (like all side effects) isn't a common or expected reaction to contrast. Either the lack of an erection is no sign at all, or a good sign that you didn't have problems with the contrast injections. No more & no less.