Q: Why am I 'hitting a wall' with sex?

What you describe--feeling like your partner is "hitting a wall" when you attempt intercourse, sounds most consistent with vaginismus. A physical exam can look normal; with careful palpation of the pelvic floor muscles, you can feel them tightening, which is what makes the "wall."

You might go back to your physician with the specific question, "Do my pelvic floor muscles seem too tight?" If that is the case, dilators and/or physical therapy are good solutions. A dilator set will include much smaller sizes--as small as a half-inch--so you can increase your comfort gradually.

Good luck! This is an issue you and your partner can work through.