Irregular period problems

Hi I have a question, I’m married wife of no babies. I want babies hopefully in the future one day. My question was, I been having irregular periods ever since I first got my period. I want to know when is a right time to take a pregnancy test when I’m trying to get pergnant. I have no idea when my period can show up. It usually happens randomly. So I don’t know exactly when to take a test because I’m afraid it will be too early or find out later I’m pergnant. Please help me what can I do?