“Terrified of having to go to an ob/gyn, looking for input?”

So although I don't identify as a girl, I am born female and I do care about my physical health. I'm 16, 117-8 lbs, 5'2, and don't use any kinds of medication or hormones, my physical health is pretty good. Maybe this started a year or two ago, I'm not sure, but on occasion (maybe a few days of the month, not including when I bleed) if I stand up to fast after sitting down fast as well, I'll sometimes get this 1 second shooting cramp in what I could best describe as the lowest part of the vaginal canal? like near the opening I guess. It doesn't affect my life in any way and 99% of the time I'm all good and things like biking don't even bother me, I'm just curious what causes this? As you can see I really don't want to go to a gyno or doctor to examine that part of my body if not necessary.