I've been reading up on the supplement threads and decided to try some of them out to see if they helped at all.
This morning around 9am on an empty stomach I took one GABA lozenge (Source Naturals brand "GABA Calm") along with one Ashwagandha root gel pill (gaia brand). Later, throughout the day, I took two more GABA lozenges and one more ashwagandha pill (which is the recommended max for both of them). I still experienced voice shakiness when having to speak in multiple classes, when talking to administrators in my department, and when talking to cashiers.
At one meeting with my advisor, though, I felt like I communicated really well and was able to express myself the way I wanted. That was only like one hour out of the day, though...it'd be nice to make that feeling last longer (and kick in earlier). But I've heard that sometimes you need to take things for a period of time before they really kick in. At this point, I'm not sure, but I'm gonna continue the routine tomorrow.
Also, I bought the supplements at Sprout's. I was talking to a guy working at the supplements department there and he said that with any supplement you buy, if you aren't satisfied with how it works, you can get your money back (even beyond 30 days). That was really helpful, because this process of finding what works is definitely going to involve trying a lot of methods/brands, and end up being really pricey.