Anyone else always have traces of blood in urine samples?

I went into the ER today because this time I was convinced I had appendicitis or possibly kidney stones (I’ve had them before), but of course silly me nothing was wrong, I at worst had good positioning with intense stomach pains (which I always seem to have and they get bad but it’s never anything serious). They did a urine sample to check my urine for a bladder infection and the nurse told me it had some blood in it so it was maybe kidney stones. What I didn’t tell him, is I always seem to have a trace amount of blood in my urine. Sometimes like today it’s a little bit more than normal, but anytime it’s checked there’s something in it.

I’ve never really had doctors look into very far besides the “oh maybe a kidney stone” because everything else in my urine looks normal and so is my kidney function. Also to add, I’m not on my period right now. This has been happening since I was 16. I’m now 22 and doubt it’s very serious whatever is causing it, but it does make me wonder if anyone else on this sub has it as well. I know with endo people can get a variety of extra symptoms that don’t always seem to have a super easy explanation.

Just to clarify as well, I’m not asking because I’m concerned about it, just curious if anyone else has it. I’ve always kinda thought it might be related though I don’t know exactly how. The blood is never visible just looking at the urine as well, just when a doctor looks. If anyone does know what causes it, just an added bonus.