Diabetes in children / undiagnosed diabetes in adults

Just wondering if there are any specific signs or symptoms that occur from undiagnosed diabetes?

A diabetic friend mentioned that I should get checked a little while ago because of some persistent health issues I was experiencing, but I never did see my doctor about it because firstly, I assumed that if I did have diabetes then it would have been discovered when I was a child because these issues are not at all new for me, and secondly, I have been unlucky enough to have had awful experiences with several doctors dismissing me on numerous different occasions, for different issues (apparently NO woman can feel her own cervix, and also “sometimes, hips CAN just...pop out of place for no reason”, who knew!) resulting in me now feeling like a hypochondriac and “powering through” whenever I’m ill or have health concerns.

Reason I’m thinking more about this now is that my 4 year old son has been complaining of pain in both his stomach, and in his penis, for a few weeks, and his doctor can’t seem to find out why. The same friend from before mentioned possible diabetes again because he also has some other symptoms, albeit very minor, and now that I’m looking into it ready to go back to the doctor today, I’m realising that I experienced a lot of these problems when I was a child, but they were all treated individually.

I do plan on mentioning this to my doctor, but because of my anxiety and mistrust I always try to be as prepared as possible and go in with as much knowledge as I can so I’m not at risk of being dismissed easily. I was wondering if there are any “telltale” signs that could help me confirm (or not) that I have grounds for thinking this may be an issue, both for myself and my son, or are there specific tests I can ask for that may not be readily offered, etc.

Thanks in advance!