I just realized the ambiguality of my phrasing which was causing the confusion. Sorry about that! Below is the sentence as I was meaning it! 
If I knew I had already had a light case that I had recovered from and was no longer contageous with and couldn’t get it again- and can’t pass it to others- I’d be more likely to be willing to volunteer to help deliver food to people who haven’t gotten it or whatever.
(Word Nerd data: In my regional version of English, illnesses are spoken of in present tense until you are well; then they are spoken of in past tense; that sentence was fine as-is for my regional dialect (with the meaning as shown in bold) but I can easily understand how in other dialects it could be ambiguous.)
