If you're asking the question, it's probably a sign it's not working. It could be the wrong drug, the wrong combo, or the wrong dose.
ALWAYS feel free to call your doc, to discuss meds. Med management really needs to be an open dialogue. What works for one brain won't work for another at ALL, or only works if you add "x" to it, but then you find you need less of "y", but with less of "y" you need to also add "z", etc.
Also, there is almost never a wonder drug. Most of the people I know on meds for anxiety/bipolar/etc...actually take several. One works as a mood stabilizer, another works for the anxiety, another works for etc etc etc. Before there was nyquil, people used to take about 8 pills on average to get the same effect...and then nyquill came out with a syrup that had all 8 alerady there in one dose. You DON'T want to do that with psychiatric drugs (for soooo many reasons), so what happens instead is that your medicines get custom tailored to suit YOU and your brain chemistry. You end up with a handful of pills...but it's just like nyquil. You only get the effect you're looking for when you add them all together.
My SIL and my best friend are both bipolar. (And then PTSD is an old friend of mine). Lexapro & Lamictl works for my best friend, but it took her a year of tweaking those two (and several others) before they found the "right" combo...and she periodically has to raise or lower the dose depending on what's going on in her life. Depakote USED to work for my SIL, but then she started having mixed episodes. So they upped the depakote, and she got reeeeallly bad. Pulled her off of the depakote stomped her with some heavy drugs to get her through a bad stretch, started backing off on them, replaced some with others, found a bad reaction in Trazidone, subbed that with something else...etc. But here's the kicker...even with all the tweaking, ALL of the depakote replacements were better than the depakote, which had worked flawlessly for years. Her brain chemistry changed after her pregnancy with her SECOND child (but not her first), so that it didn't react well with the depakote.
With both my SIL and BF, they were on the phone almost daily with their docs to touch base, and a weekly appt. for the first several months. Once they had a pretty good combo worked out, the phone calls and appts started having more space between them, until now...they only call if something starts to feel off.
So yeah...it's completely common and expected for people to have different reactions to the same drug, and for your own doseage needs to change as well.