Feeling dizzy, nauseous, and vomiting after runs + leg pain... help!

Hey there!
So, here’s the deal: I play soccer during PE class, right? I’m running around just like everyone else, but after only five minutes of playing, my head starts spinning like crazy—it feels like I’m actually going to pass out—and then the nausea hits...
Last time, I had to bolt to the restroom to throw up. Once I finally got it all out, washed up, and grabbed some water, I felt like a brand-new person and finished the game without any issues at all...
The catch is that this happens every single time. I make sure to eat breakfast before school every day, and honestly, I don't really do any other sports; I have a pretty sedentary lifestyle. I'm 17 years old and, I don't know, I feel like this isn't normal at all, even if I am totally out of shape. I'm about 5'10" and weigh around 138 pounds. What do you guys think could be going on?

My other issue is my leg... specifically the back of my right knee. I think it might be the ligaments or something. It just starts aching while I'm sitting down or standing for too long, and the pain won't let up until I prop my leg up on another chair so it's horizontal. Only then, after maybe five minutes, does the pain subside, but then my lower right leg goes numb. Like, I can scratch it and feel absolutely nothing. It’s a deep, internal pain, not just a surface thing. I've been dealing with this misery every single day for two years now...
One thing I noticed is that when I was 15 and only 5'4", I didn't have these leg pains. But once I turned 16 and measured myself, I was 5'8". That’s a 3.5-inch jump in just one year! That's when the leg pain started. Could it be because I grew way too fast?
Thanks in advance for any help!
I'd upload a photo so you could see exactly where it hurts, but this stupid forum won't let me upload anything larger than 9.8 kb. Total pain in the neck.

Look, while you're waiting for us to weigh in, go see your doctor and run through all of this. Dizziness can just be low blood pressure, and throwing up after pushing yourself too hard isn't exactly rare. So, did you actually overexert yourself enough to trigger the nausea? 🤷 It’s probably a mix of different things at play here. Long story short: see your physician on Monday, get the referrals for some tests, and once those results come back, let us know what's going on. Just keep the link to your current thread handy so you don't start a new one.
At your age, anything is on the table. 😁

It wasn't even that much of an effort, really... maybe just two or three minutes of sprinting... I get the exact same thing when I'm out cycling. You know, you're grinding it out uphill, and instead of feeling the burn in your legs, I suddenly feel this intense lightheadedness in my head. I actually turned pale! I had to sit down for five minutes just to recover. I checked my pulse while sitting on the bus, and it was hovering right around 100 beats per minute.
I’ll make an appointment with my doctor once my schedule clears up—probably sometime next week—and then I'll let you all know how things are looking.

So, they’ve been sending me all over the place, and now they're acting like there's some kind of issue with my leg... I'm heading in tomorrow to get bloodwork done at the lab, and then I've got an ultrasound scheduled in Chicago.

Ever actually managed to track your blood pressure, like, before and after hitting the gym? (not just checking your pulse)