Could it be pinworms? If not, then what?

For the past few days my butt has been itchy. Not unbearable or anything, but noticeable. I am soo worried that its pinworms. And then today my stomach kind of hurts and I got diarrhea. My butt is mostly itchy towards the top though, like toward the crack and not as much near the hole (although its there too). Theres also a rash that goes from the bottom to the top of my butt. Do you think this could be pinworms? I have have like a red streak on my genital area and it hurts when I touch it, but this could be completely unrelated. I dont have health insurance so i dont really want to go to a doctor until im sure. Ive looked with a flashlight and in my stool, but i havent seen anything. I know of an over-the-counter medicine called pin-x. Is this safe to take even if I'm not 100% sure that I have pinworms. Does it really work? If its not pinworms, what could it be? Does it sound like something that could go away on its own? Is the diarrhea and stomach pains just some random event (although i read that in rare cases pinworms can cause this)? Thank you so much in advance!

[Meghan1186]

oh, also when i shower if i make it so that the water touches the upper part of my butt where it itches, it burns and hurts a lot. but could this just be because ive been itching it a lot?

[Meghan1186]

oh, andd is the itching at night from pinworms supposed to be REALLY bad. because its bad but not horrible or anything. like it doesnt wake me up or anything like that. and when this started it was when i went to the bathroom, went back into bed and the upper part of my butt itched SOOOO bad. i scratched and scratched, but it wouldn't go away. Finally I got up and used tiolet paper to itch it and that seemed to fix it. Sorry I have so much information/questions, Im  just soo worried about pinworms.