Embarring Period Predicament?

I'm on a field trip with science club right now. We're spending the night at this huge zoo and learning all about animals, and it's been pretty fun so far. The problem is that my period just started, and I seriously just had it 2 weeks ago, so I'm not prepared at all. I put toilet paper in my panties, but it keeps getting heavier. I've been running to the bathroom a lot, and for the past 2 hours or so, I've had cramps really bad, so I've just been laying around in my beanbag working on my worksheets curled up in a ball. I've asked my friends if they have a pad or tampon, but none of them have any with them. THere's a machine in the bathroom, but it's out of both pads and tampons. We have 2 supervisors. One's 65 and the other is 44. I'm pretty close to the older one. I think she thinks something's up with me, because I keep running to the bathroom and she keeps asking me if I'm alright. I don't know if she knows or not...but I think she does. When she asked me if I was sick, I told her no, and kinda changed the subject becuase I was embarred. I know I need help...we're not leaviing the zoo until at least 3 o'clock tomorrow afternoon. I guess I don't mind telling her what happened, but I don't know what to say. I'm just really embarred and I don't want everyone to know...but at the same time, I don't want to keep running to the restroom every half an hour. There's a HyVee about 10 miles from here..I can't drive, but should I see if she can take me to go buy some tampons? And what should I do about the cramps? I don't have any meds with me, and they're really bad. Should I tell my teacher al of this, and if yes, how so?