Q: Why am I too tight for sex?

What you describe could well be vaginismus, which is the involuntary spasm of pelvic floor muscles of the outer (lower) third of the vagina. The resulting interference with intercourse is experienced as "too tight," "he can’t get in," or "it’s like he's hitting a wall."

Because the spasm is involuntary, the cause is sometimes difficult to understand. Pain in the area of the pelvis can be a contributing factor, so the hip pain you describe is likely involved. Beyond interfering with intercourse, vaginismus--those pelvic floor muscles in spasm--can also be experienced as pain in the pelvis, low back, low abdomen, and upper thighs.

It's important to have an exam to better understand what's happening for you, and I'd advise that you have the exam sooner than later. If you have surgery in your future, physical therapy that starts before-hand (and continues after) could help in your recovery, too. Vaginal dilators are often a part of therapy for vaginismus, and that, too, can start now and deliver benefits for your recovery.

Good luck in working through this! With patience and good information, you can do it.