Just a quick interjection here....multiple times??? In other words, you allowed yourself to get in a situation with this person outside the workplace more than one time where he tried to force you to have sex with him, and you did nothing, and got in the situation again where he tried to force you to have sex with him, etc. Makes the story sound a little weirder. I'm never in favor of not reporting and filing and complaining about any form of sexual harassment, but this isn't coming through clearly.
Have you had any problems with this person in the workplace? Is there anything going on that the employer should be aware of? Is the coworker clearly aware that you do not find these advances appropriate? Why, really, haven't you called the police and filed charges against him for assaulting you in this off the job situation?