When do I test

my fiance have been TTC for about 3 months now, it my periods have been acting a little wacky these last couple years.

I haven't always had regular periods. I actually started taking natural supplements to help me get them. and luckily I did! I've had one the last 2 months like clockwork. well today I'm supposed to start again. and its not here. which I'm assuming is like usual, it's just not here. but I want to take a pregnancy test, but not too early. when is the best time for me to take one? thanks everyone!