I have several questions on pulmonary Anthrax

How likely is it to happen via mail?
If the letter was open would I get immediate symptoms?

I've experienced chest pains and other symptoms since 3 weeks.
I've got chest two chest x-rays in a 2 weeks span, one 3 weeks ago and 1 last week checked by 2 different doctors and 1 x-ray specialist

If I would have pulmonary anthrax would the doctors have seen it?

I got my white blood cells check 3 weeks ago it was normal

Now I've got the flu, for 3 days I'm not feeling well but no temperature and normal high blood pressure.

Can somebody clear things for me on anthrax here?