Troubles.

This all happened about a week ago.

I've been dating this girl for a total of 5 months, and I have gotten multiple hand jobs/blow jobs from her, but never gotten off from them. I masturbate around 3 times a week (sometimes more/less). She's amazing at giving bjs too, they feel amazing, but I just can't get off to them. Anyways, about a week ago, we had sex (my first time, her like, 3rd time so she knew what she was doing) and we went for over 15 minutes, and it felt amazing, but I just never felt like cumming. She then had to leave, so we had to stop. It was embarrassing to say the least, is that weird? Everyone else I've asked say they only lasted under 2 minutes on their first time.

Whenever I do masturbate, I can do it in under 2 minutes.

I'm also very comfortable around her. I'm thinking of just not masturbating for till I cum around her, as I'm starting to think she's thinking that I'm just not turned on by her, which I am.

My question boils down to, is that a bad thing for lasting so long? Is this just proof that I'm not ready? (I hit puberty in sixth grade, by the way....)