It's very awkward to say the least. The bottom line is: A native English speaker will probably never form a sentence like that, at least not to mean that you became ill two days ago. The sentence as it is used would need a context, but could mean "Something that happened two days ago has made me sick." Rather than comment on the tense, let me give you a few ways that are much more natural. When we're speaking, most often it would be: I've been sick for the last two days. Or: I've been ill for the last two days. If it's known that you are still sick, or it's not important in the context whether or not you are still sick: I got sick two days ago. Or: I became ill two days ago. Another alternative that is a little more colloqial, but is still used: I came down with something two days ago. I got a bug a couple of days ago.

I you mean you were ill two days ago and are still ill now, the best way to say it is "I have been ill for two days." You can also say "I have been ill since the day before yesterday/Tuesday."