from smoking i would say most people only get anxious for a couple hours and then come down.
if you are feeling anxious for days that sounds kind of unusual. you can only experiment and see how you feel. other people's anecdotes about how a drug like weed affects them are gonna be kind of useless cause everyone is so different.
do you feel relief with the weed for a short time and then get anxious when it wears off a bit, or is this like you are just greening out from the initial high?
i find stuff like how i sleep with the amount of hours and even the position i sleep in, how hydrated i am, how i feel naturally just with my breathing, all this stuff can kind of change up my high A LITTLE BIT, but for the most part weed is just like a specific feeling that i always translate with relief.
also if you have any way of knowing which strains you are getting, maybe that can help you a bit. some people get a bit anxious from indica or sativa.
i would think taking a tolerance break is gonna make you more sensitive to weed, and some people find that initial rush to be anxiety inducing.. usually when people need tolerance breaks it's just cause the weed is leading them to feel shitty and tired from what i've heard described, but then again everyone is different. maybe you feel under the weather from the weed and that is causing you to feel anxiety. i wouldn't really suspect that, but maybe..
also if you frequently take benzos, i notice when using downers i tend to crave them and my marijuana highs aren't really as good when i don't have any of the downer i've been taking.