When to test for pregnancy?

First of all i have irregular periods! my last period was april 18th. sometimes i don't have periods for 2-3 months. I have had cramping the past week, but no period, i do seem to pee more, but i have problems with overactive bladder. my back is killing me, but that's a pms symptom. the last time i was pregnant i has severe morning sickness ( unfortunately i miscarried) i don't have any sickness now, just an upset stomach every once in a while. also my belly button ring has been hurting a bit and i never had problems before. my question is when should i start testing since things are kind of out of wack. I did see my doctor and she put me on birth control to regulate my periods, but since were ttc that wont work this time.