When to take clomid

My doctor prescribed me clomid to help me get pregnant because I have PCOS. He explained to me to take it in the 5th day if my cycle for 5 days. However my periods have always been very irregular. I took the pills 2 weeks ago when I got my period but now I’m spotting again and seems like I might get another period. Do I take the clomid again or wait and hope I get my period next month? I’m just not sure how many times a month I can take it. Wondering if anyone has some insight.