Don't know when to start using conceive plus?!

I'm having ovulation pains as usual but negative test results, Im waiting to use conceive plus and mucus cough for the first time but I don't know when to start using them, would it do any harm to start now or should I wait for a positive ovulation result?? Worried I'll start them too late, my cycles are irregular at the moment so not sure when to expect ovulation.