Spend more time enjoying clitoral stimulation to orgasm after orgasm with masturbation.
Everyone who struggles with sex on a physical level encounters this bias.
Women must learn to take control of partnersex and "Run the Fuck".
You need to be masturbating regularly with your preference for clitoral stimulation while practicing vaginal penetration.
I suggest you take control of the situation by devising your own more natural approach.
Since you are orgasmic with masturbation, have an orgasm right before he begins to penetrate you.
Taking it slow is important AND only adding vaginal penetration AFTER she is fully excited with clitoral stimulation PLUS using some additional lube.
I suggest you begin at the beginning and learn about your clitoris and spend some time masturbating.
Time for you to shift over to alternative medicine and healing.
Your GF can begin to practice expanding her vagina by using the pelvic floor muscles during masturbation.