That "shaky and gaggy" feeling? That is your gut telling you this is a bad idea. You don't have to answer the phone, sweetie. You can take yourself out of there for a while and do some activity that is only ALL about YOU. Just answering the phone gives him the satisfaction that he is still in control, that nothing has changed, that it will only take a few more sweet, empty words from him to get you right back where he needs you to be so that he can continue his addiction. Think of it this way, with the whole "If nothing changes, nothing changes" mantra. Not only are you finally pulling yourself out of that vicious circle, you are letting him face the consequences of his own choices, and he will only have himself to blame when his addiction brings him more pain.
Hang tough! Put your hand palm out and say NO MORE.