happened half an hour ago:

I asked over this girl I've been dating for while. I asked her over to watch a movie late at night. We start to kiss, I end up fingering and going down on her. She's really into it. Me however, I can't get it up. Maybe a 75% erection at best. It's been a very very long time since I last had sex. She starts to give me a blowjob. I still can't really get it up. We start to kiss again. At one point however as I'm stroking myself, I cum, very unexpected, with that same 75% erection. I act as if nothing really happened (i'm not sure if she saw it), and I start to go down on her again. Now it's really really impossible to get it hard at all. I'm bummed out, I didn't want to disappoint anyone.

At one point, after having going down on her, fingered her, kissed her, she ends up on top of me. I still can't get it up. I stop, look her in the eye, and tell her "don't take this the wrong way, but I think you should leave". She looks at me a bit confused, asks, "are you OK?". I tell her "yea". I get up, and walk to the bathroom. She's getting dressed. As she leaves, I say "don't worry about it, ok?". She tells me "sure okay".

To make matters worse: she left my apartment all by herself, to go take the train not too far away at 10 PM. I don't live in a ghetto, but it's still a big city. I don't want anything to happen to her.

To make matters even worse: she's throwing a party tomorrow. I've never been to her apartment. I don't want to make things awkward. I feel like absolute shit now, I've let myself and her down, and I can imagine things turning out very awkward tomorrow.

I really don't know what to do at this point.