Sorry you and lo have been unwell. I agree, your bm won't be making your lo sick. A couple of years ago I too got a bug like that and my dd1 did not get sick at all. Meanwhile everyone else around me was falling ill to it, seemingly by just being in the same room for a few minutes!! It was extremely contagious. Luckily my dd1 had my antibody-filled milk to keep her well.
I just had a thought that if the ebm your lo was drinking was from before you got sick, then it won't have the antibodies in it from your illness yet.
However, any antibodies that you can pass on to him will be helping him get better quicker, even though he's already sick.