This has happened to Martel, definitely not to the point of cracked and bleeding, but he gets dry skin which sheds. However, his is from masturbating dry and not necessarily from having sex. So, are you masturbating a lot in addition to having sex? If so, do you masturbate "dry" (no lube)?
Personally, this sounds like a more serious issue- your penis shouldn't bleed. When's the last time your girl went to her OBGYN? She might have an infection (not an STD, just a regular ole infection) that is affecting the secretions of her vagina. You should go to your doctor and her to hers and both get checked out. The doctor is the only person who's going to be able to tell you definitively what is going on.
Bottom line: Get both of ye to thy doctor!
__________________
Sage knows our mythic history, King Arthur's and Sir Caradoc's
She answers hard acrostics, has a pretty taste for paradox
She quotes in elegiacs all the crimes of Heliogabalus
In conics she can floor peculiarities parabolous
-C'hi