Why do I not come during intercourse?

So last night I had sex (for the first time) with the most beautiful girl I know. I used to be a chronic masturbator but have been more infrequent in the past year and would come in a couple minutes. I do the dirty with her (oral + vaginal) for a good 20-30 minutes (wasn’t keeping track) but I noticed that I couldn’t get fully hard and didn’t come by the end. I felt pretty embarrassed by the end but she took it pretty lightly (though still feel guilty tho). I’m gonna see a doctor tomorrow for an unrelated checkup, but I’m wondering if anyone else has gone through this or what I should ask my doctor?