Is this heat exhaustion?

I was at the water slides yesterday, and it was cloudy, so I thought I wouldn't get burnt... So I didn't put on sunscreen. I certainly learned my lesson. Anyway, my friend says that I might have heat stroke...But I don't think it's that bad. I think I might have heat exhaustion because I'm irritable, extremely tired, kinda dizzy, restless, nauseous, and I have slight headaches that come and go.