Panic like symptoms BEFORE pooping

Hi there, So, I can quite happily be going about my day when I suddenly get this weird feeling, like a sinking/doom feeling, I then get very hot, start sweating (hands, feet), feel dizzy, short of breath, shaking, I have difficulty standing, brain fog and crazy fast thumping heart followed by needing to poop. After I have pooped I continue to feel bad for around 20mins and then everything goes back to normal as if nothing ever happened. It's awful and ruining my life, doctors always say it's vagal because I'm straining, they never listen to the fact that this happens way before I'm even in the loo. Anyone else?? Xx