Hi,
You could call Susan G. Komen for the Cure.For information call: 1-877 GO KOMEN and hopefully they will suggest to you where to go for a free Ultrasound test in Colorado.Also you could call the American Cancer Society at 1-800-227-2345 to see if and where there may be assistance available in your area.
I hope you'll find some help soon.
Take care and I wish you well.
The Health Department in your locale will most likely have mammograms and ultrasounds available or can at least point you in the right direction. I've never heard of an ultrasound being done before a mammogram though.
Best wishes.