I think most natural probiotic foods have strep so you shouldnt worry about it. Strep is only dangerous if its overgrown. Actually any beneficial bacteria is dangerous overgrown especially bifidobacteria.
The best bet is for you to make kefir from kefir grains or try some sauerkraut. Yogurt has way too much Sugar and will make you worse. Only buy yogurt if its made from raw milk with no Sugar added.
I'm also not understanding why supplements give you anxiety. Maybe your having a allergy?