I don't know either, but I got shingles about exactly the time I must have conceived DS, and then a nasty stomach bug when about 7-8 weeks pregnant (lost half a stone - eek!). It is hard not to worry, but GP told me would be fine and he seems to be okay at 5 months old. Was after a mc for me as well, so do understand how you worry.
When I was 24 weeks pregnant I caught the norovirus bug (very nasty stomach bug). Vomiting and diarrohea for days. My obstetrician told me that the baby would be fine, the only risk was if I got dehydrated. So just make sure that you stay hydrated, with lots of fluids and possibly rehydration salts if necessary. Ordinary illnesses very rarely cause mc especially early ones.