[Some1]

Hey. So I'm a guy, 17.

Me and a friend(girl) have planned to "hook up" for a while.
So a few days ago it was gonna happen, we planned to meet the previous day.

I was turned on during foreplay stuff.
While i was giving her oral(which went well) my erection went away.
Then it was my turn, she touched my penis and nothing really happened.

We tried kissing for awhile, i stroked myself and got kinda hard.
But as soon as she touched it again I lost it.

I think i might've psyched myself out a bit. I was thinking about what I should do, when to do what, how well I was performing.
I didn't get into it and lose myself in the moment.

I wasn't drunk during. I drink sometimes and and smoke weed pretty regularly. I just started smoking a little tobacco.

Im not gay, and I am attracted to this girl.

I masturbated early that day, thinking it would make me last longer.

So if anyone has any advice that would be great. It was pretty embarrassing, she said it was "ok".
We've been pretty close friends for a little while.
I really don't know what she thinks.

I haven't talked to her about it yet, I want to.

What should I do next time?
Could I have a physical problem?