I (F19) constantly faint when overheated, needing some advice!

I (19, F) have had issues with fainting over the past few months. The first instance was at a concert in may, I was standing with some friends and within 20 seconds I was on the floor. This first time I don’t know how long I was out for, it felt like I’d had a whole nights sleep. I thought maybe I’d just gotten to hot so I got some water once feeling better and stood where I have space. Throughout the night the feeling of fainting must’ve happened another 2/3 times. I feel like I don’t recover from it until I am able to properly lay down for a longer period of time.

The second instance this has happened was in embarrassingly the security line at the airport, however this time I do not remember feeling like I was about to faint. It took about 10/15 minutes for me to feel strong enough to stand up. Even after I had stood up my hearing was slightly skewed and I was extremely shaky. The same feeling happened to me on the return flight to the airport, however I managed to hold myself up for long enough to find somewhere to relax.

The feeling of it seems to happen the second I get a bit too hot, I also know that I worry about it happening so I try to prepare as much for it as possible. I don’t know if it is to do with crowds or just heat but it is beginning to happen more often than not. I know I have quite high blood pressure for my age too, so this might also be a factor? There has been plenty of times recently where i get a hot flash and I have had the feeling overwhelm me but I have managed to cool myself down and relax and eventually I feel a bit stronger.

Just needing some tips and advice on what I can do to overcome this as it has impacted lots of activities I want to do as I know I will faint. I drink plenty of water and have electrolytes on hand now too! Thank you :)