What else could cause short breath, feeling faint, and nausea?

So I’ve been to the doctor a couple times and had a bunch of blood tests done for my thyroid, electrolytes, hemoglobin, vitamin/mineral deficiencies, and everything came back normal.

I have PVC so I don’t know if that has to do with it but the cardiologist and electrologist said everything looked normal.

I don’t know what else could be the reason. If it’s because PVC then I just have to live with it. They’re not really sure why I feel this way, could it be because of the constant heart palpitations? I asked if I needed a catscan or anything but the doctor doesn’t think it’s serious.

Could it be low blood pressure? I’m on the low side but still normal. I’m just sick and tired of going to the doctors all the time.