I can't say I know exactly how you feel, being a guy, but I experience similar moments. I know that what I have is anxiety. I've had numerous blood tests,cat scan, mri, etc., and it all came back clear. But still, every now and then I'll get anxious, heart palps will kick up, the random pains will start, and I'll start doubting everything. I consider myself decent at self control, but it still takes all I can do to calm down.