I have been experiencing shortness of breath

Sorry, English is not my first language.
I'm 17
I’ve been dealing with these symptoms for about 4 years now.

It all started back in school. I was sitting in class when I suddenly felt discomfort and a little shortness of breath. It wasn’t too bad, and after a few minutes it went away, so I didn’t think much of it.

About a week later, I suddenly had really intense shortness of breath that I couldn’t handle. The strange thing is, it got better when I stood up from my chair. I told my parents, and they rushed me to the hospital. That whole month, I went through tons of tests from head to toe, but they found nothing wrong. In the end, the doctors diagnosed me with anxiety.

At the beginning, I was also extremely sensitive to sounds and lights like I would get startled by almost everything. Thankfully, that part improved over time.

A year later, while walking to school, I felt a weird jitter in my chest, almost like I wanted to cough or like something was stuck in my throat. It felt odd, but I ignored it. Then a few days later, out of nowhere, I felt like something grabbed and squeezed my heart. It was painful, like heart hiccups, and honestly terrifying.

Now it’s been about 2 years since then, and I still get these symptoms. Tonight is especially bad I can’t sleep at all. Every time I start feeling sleepy and yawn, I get shortness of breath. When I lie down, I just can’t breathe properly, and it’s 3 AM right now. I feel so desperate I could cry. Please help me how to get rid of this