Confirm suspicion or Quiet fear

On 1/21 while showering I found what felt like a large

[H. Hunter Handsfield, M.D.]

This sounds like an infected sebaceous cyst or folliculitis.  If just inside the vaginal opening on one side or the other, I would worry about a Bartholin gland infectin, which can be a sign of gonorrhea or chlamydia.  This surely isn't related to the cramps and probably not to labial itching.

So this doesn't sound like an STD.  I don't know your partner; you are a much better judge of his fidelity than I can be.  However, when I lecture to health care providers and talk about how to judge STD risk, I give 2 scenarios about the relationship when a patient may or may not have an STD:  "Our relationship is strong and I just don't believe for a minute he has had other partners"; and "I don't think he has had other partners, but you just never really know, do you?"--almost exactly the words you used.  Which one sounds like the greater risk?

So if you indeed have reason to doubt your partner's fidelity, it can't hurt to get tested for common STDs.  But I don't believe an STD is causing your problem.

Good luck--  HHH, MD