Need some anatomy lessons...
 

During intercourse with my now ex-wife, I would only be able to partially enter her. It felt like I was hitting something inside. Eventually that something would open or relax and allow me to enter all the way. I am just wondering what that was. If it matters, I am seven inches long (typical, a guy having to say how big he is!).

Thanks for your help.

I haven't ever heard of this problem unless you weren't performing enough foreplay to allow her to relax and self lubricate.

I think that may be the case. If I can remember back to my teen sexual encounters.... I seem to recall feeling like that when having intercourse early on, half horny, half nervous...muscles tightened. Since your size is average, I would suspect it to be tension but I am certainly no doctor.

http://www.med-help.net/VaginalProblems.html

Might check out vaginismus...sounds similar to what you experienced with your ex.

Crap I have heard of that. Damn it's been so long since I posted on a sex message board I failed to do a little search.

Sounds to me like her PC muscles were contracted.

I don't think there is any way he could not enter just because she was contracting her PC muscles. Some womens are strong, but I dont think that strong! lol :D