Not sure exactly what to tell you because recovering from any form of sexual assault is deeply personal. I think you get this already but just to reiterate: he raped you and it’s not your fault. At all. I know you feel shame over this but it is not on you and I’ll explain why.
James’ actions as you describe them and as his roommate related are pretty classic for a serial rapist. He ignored you until you were drunk, he then presented himself as “safe,” waiting until he got you alone to drop the mask, he did not even attempt to get consent and when you said no he called you a liar, and then he didn’t follow up with you in any way. The roomie saying that James get’s weird when he’s drunk and is a “nice guy” means that James has done this before. So, no, James wasn’t that drunk. His inebriation wouldn’t excuse it anyway, but he was playacting.
James is a monster.
You did nothing wrong. You had an expectation of safety, you had a plan. This guy removed you from a relatively safe situation where you had some control with the intent of raping you. He might not have had specifically you in his sights when he went to that party, but he was planning on raping someone.
Lastly, thank you for sharing your story. I know it’s tough, but the more women who expose serial rapists like James the more we’ll be able to put them in jail where they belong.