You say you reached menopause (one year without a period) six years ago. Sex has become painful, and you want to “get it back.”
It’s never too late! Using a vaginal moisturizer may be of some benefit, but if you’ve had pain for several years, you may need a prescription treatment option to restore comfort. There are localized estrogens and Osphena (a non-hormonal option) that are very effective at restoring vaginal health. I have a patient who had not had intercourse in over 25 years. Within 3 months of treatment she was able to resume--and enjoy--intercourse! It is absolutely possible.
I would recommend going to a physician/provider who can do a careful exam and confirm the cause of the pain. Atrophy is the most common reason for painful intercourse after menopause, but there can be other causes as well; identifying the right cause makes all the difference to effective treatment.
With effort and follow-through it is nearly always possible to successfully restore the ability to have intercourse.
What you ask about specifically is your clitoris, which, along with other genital tissues, does typically shrink with the loss of estrogen—whether through menopause or some other medical event. Because you're under 40, which is young for what you're describing, I'd encourage you to express your concern to your health care provider and have a thorough pelvic exam. The exam will be helpful in finding out whether there's another vulvar condition causing the tissue changes—or whether you're experiencing normal changes.
As we lose estrogen, we do face something of a "use it or lose it" proposition. That is, circulation and stimulation keep our genital tissues healthier; left to their own devices, they'll atrophy. If you don't have a partner right now, a vibrator is a great choice to provide stimulation and increased blood supply to the area. Maintaining your health means you'll be ready for intimacy when—just when you least expect it—a relationship emerges!
You say you don't have issues with vaginal dryness, but you did feel discomfort--difficult to sit comfortably, spasms of pain--for at least a week after intercourse. It does sound as though you experienced some trauma.
It's likely that though you're still experiencing your own lubrication when stimulated, you're experiencing some atrophy, too. I'd suggest that you start using a vaginal moisturizer (like Yes or Replens) or a localized estrogen to maintain moisture all of the time--not just when you're aroused.
If you and your partner aren't able to be intimate often (and I'm afraid the definition of "often" varies from woman to woman), you might think about some of the additional options I talked about in a blog post about "Staying Ready for Sex." It's easier to maintain your sexuality than to restore it!