There's no way of putting a percentage on this without knowing the complete picture. There may be many reasons why DNA may or may not be found (he may have been wearing a condom) and even if DNA is found, there is still the defense claim of consent. As a former sexual assault prosecutor, I can tell you that each case is different and each turns on the relative credibility of the parties involved. Trial work is a art, not a science and there's no way to assign a percentage to the chances of conviction.
There's way too little information here to provide a meaningful answer to your "what is the chance..." question. I assume you sought immediate law enforcement and medical assistance. If this is correct, simply rely on law enforcement to pursue the matter. The case resolution will depend on the availability of admissible evidence of the allegation. Were there third party witnesses; did defendant make a statement to law enforcement; what is the content and reliability of your statement; ect? It's unclear why you believe you were raped if you were unconscious during the whole episode but surely this will be an issue that arises if a case against the defendant is brought by the DA.