Penis hitting a wall of her vagina and she's experiencing immense pain

Hi, I am an average sized guy, i have a 5.8" penis length and 4.7" girth. i have had sex with 2 girls, 1 my wife and 1 my gf 6 years back. my gf enjoyed sex and we had no problems at all while i penetrated her deeper in supporting positions. however since i got married and my wife and i had sex, she experienced immense pain. at first i thought since she is a virgin she will settle down but after 4 weeks i managed to penetrate fully. Now we are having sex regularly but i cannot penetrate her deep, if i do it feel as there some kind of a wall at the end of her tunnel. my penis keeps hitting it and starts to get painfull for me. i have no idea why. i need to know what is that wall and how can it be so close like 5.8" if i assume i penetrate her fully.