If I say "Every time I eat crabs, I feel sick" (it is a usual fact that will last all my life.)
But is it possible to say "Every time I'm eating crabs, I feel sick." Does it change the meaning of the first part of the sentence? when I say that I am not necessarily eating crabs right now.
Would it be possible to say "Every time I'm eating crabs, I'm feeling sick", what would that mean... a temporary situation ( won't last all my life.)
Whenever I eat crab, I feel sick afterwards.
Or
Whenever I've eaten crab, I feel sick.
The last tense I'd choose would be the progressive, unless I wished to imply that the sick feeling comes over me while I'm having the meal.
Whenever I'm eating crab, I begin to feel sick.
An important thing to bear in mind here is the sequence and nature of the actions. As we can see from the last example, the sick feeling can be an incipient feeling (begin to feel). In the first example, using the present tense, we have habitual action; to make abundantly clear that the sick feeling is the result of eating crab (and not the reason for eating crab), we use afterwards.
Whenever I eat chicken soup, I'm feeling sick.
In the case of the chicken soup, it is eaten because you feel sick. The implication is that you don't normally eat chicken soup, and treat it as a remedy.
It would be possible, but we don't.
There is no meaning added by using the present continuous in this example. In fact, using "every time" makes it clear that you are not talking about now, so the present continuous is inappropriate.
The repeated use of the progressive form is usually used to indicate immediacy, usually as part of an informal sort of storytelling.
"I'm visiting my in-laws, see? And every night they feed me these really good crabs. And every time I'm eating crabs, I'm feeling sick. And then it hits me - they're trying to poison me!"
Contrast this with a more standard use of tenses.
I went to visit my in-laws, and every evening we had excellent crab dishes. I soon noticed that every time I ate these great crabs I felt sick, and I realized that my in-laws were trying to poison me.
