When your penis is too big
First up, you should steer clear of rear-entry positions until your lover is well and truly wet; both naturally and with tons of lube. If she's not ready for you, you'll only hurt her by entering prematurely in a rear-entry position. Always keep a juicy lube to hand, such as the ID Glide Lube Squeeze Bottle, Liquid Silk Lube or the Good Vibrations Please Gel Lubricant.
Foreplay is a must for well-hung guys, so be sure to devote plenty of time to going down on your girl and bringing her to orgasm before you have sex. Her vagina will expand a lot more when she's aroused, making more room for your gigantic penis to enter her comfortably!