False positive FOBT?

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25F. 152 cm. 40 kg. Birth control pill, antacid.

My doctor recently prescribed me a FOBT following my complaint of diffuse abdominal pain, which I now believe to be a mix of birth control related cramps, stipsis and gas.

He made me do an ultrasound, which came back mostly normal, except the doctor described a "pouch of free fluid among the intestinal loops", which alarmed my GP, who, in turn, prescribed me all these tests saying my colon is inflamed.

Now, I'll be a doctor very soon, and something about the ultrasound and this whole thing seemed wrong. Turns out, I was right. The pouch was actually a Nabothian cyst, as later confirmed by a gynecologist.

I did the tests anyways. Fecal calprotectin is negative (<3). One of the FOBT samples is positive though (0, 0 and 119 ng/mL). I distinctly remember the day I took my last sample, the positive one, my birth control pill related spotting had just started. It was very little, but it was there. I in fact even saw a brown drop near to the stool I used for the test. Unfortunately, my spotting is unpredictable and I didn't expect it that day.

I told my doctor, he didn't listen and sent me for a colonoscopy. I think it's a bit unnecessary and that this is a plausible explanation as to what happened. What do you think?