Extreme Heat Exhaustion??

Hey guys. I'm actually a current pre-med undergrad student, but I'm coming with a personal concern. I 20(f) have dealt with extreme heat exhaustion for as long as I can remember. This happens mostly in summer, but can happen throughout the year.

My symptoms: extreme exhaustion and faitgue, feeling faint, low blood pressure, headaches/migraines, dizziness, nausea, thumping heartbeat that is fast and weak (but i can physically feel it, if that makes sense), weakness. Basically, all of the symptoms of normal heat exhaustion, but worse. Sometimes my heart can palpitate.

This usually happens when I'm outside for a prolonged time, like theme parks or zoos. I hydrate regularly and more so during hot and humid days, so being dehydrated isn't the problem. I get super grumpy and snappy when I get like this, but I LOVE theme parks, zoos, etc. It gets difficult because I feel like I could pass out at any second during these moments, and i feel bad for anyone I'm with. It doesnt help that I have ADHD, so I'm usually energetic, but I can't be my normal self with this heat exhaustion.

Could this be a larger issue? How do I address this with my doctor, without them dismissing me? Any advice and recommendations welcomed!