Help ttc!

Rachel

So I have irregular periods, I've been trying for a baby for about 7 months now and still nothing. I've missed my period for almost 3 months but I've took 2 pregnancy tests about a week ago and they both said negative. (First response - pregnancy tests) I have decided to buy some ovulation tests, has anyone used them before? Does anyone know when the best time and what days should I use them?