I have a sinus infection, I'm on day 2 of amoxicillan. Now my face feels more stuffy, but less pain in my sinuses. Does this mean the meds are working?

Amoxicillin not 1st. Amoxicillin is not my first choice of antibiotics for a sinus infection. It sounds like you are responding, though. I would prefer Augmentin (amoxicillin and clavulanate) (Amoxicillin + clavulanate) - your symptoms should clear in about 7-10 days. I many times add a steriod pak when i treat for sinusitis. Also add some over the counter afrin (twice a day) for the next 3 days as well.
Decongest, expector. Agree with dr. Melder. And dr. Bowman. May benefit from expectorant (guaifenisen) to thin out mucus; nasal steroid spray can help decongest, without systemic effects, without effects of nasal or oral decongestants that shrink vessels (bp problems, anxiety, palpitations, prostate issues, etc).