Info for medical assistance

I am in a strange situation, in need of a colonoscopy. I am unable to work, and have been turned down by the gold card since i am unemployed, but not homeless, and do not have someone supporting me. I have no insurance and have no idea where to look from here. The ER referred me to the gold card clinic, and now being turned down i don't know if there is anywhere else to look in houston. If anyone can point me in the direction of some assistance or any info at all it would be appreciated.