Why is it so hard and takes so long for me to?

To "O" during oral unless he goes REALLY fast (As fast as a vibrator lol) Or unless he's inserting something in my V. In those cases, it doesn't take me more than 2 minutes to "O" But without him going fast or inserting his finger inside and just playing with my "C", it takes like 20 minutes. Is this common? I know it's normal, but are most women like that?