Miss jojo, no one is a perfect muslim and imperfection means that we all have doubts about this or that. That should not stop us from promoting what we do not have any doubt about .. and that is dawa. So no, you should not stop dawa just because you ar econfused about this aspect of Islam.
BTW, Islam did not invent polygamy but its unfortunate that Islam gets the blame of it. Islam just restricted it to 4 marriages. Jews, Christians and followers of deen-e-ibrahimi of Prophet’s time were already practicing it.