Dating Laws in Colorado?

Alright. I know there has been plenty of debate over this topic but I have yet to reach a clear enough answer. I'm 15 years old as of March 18th. I met a guy who I've been having a relationship with who is 20 as of April 27th. We get along fine and our relationship is healthy. The topic of sex has come up and we don't want to risk breaking any major laws. People have said a million times over that it is completely illegal in every state for someone 18 years of age and older to have sex with a minor. (someone under 18). Yes, I've heard that there is no true law against dating, only against having sexual relations. But, upon further looking I've found that I would legally be allowed to consent to sex as long as I was at least 15 and he was no more than 10 years older than I was. Do correct me if I'm wrong. I don't want any guesses here. I want straight out of the book answers. And if you could site your source of this information I would greatly appreciate that. (: Thanks.