First round Clomid-- Day 21

Hi ladies! I've always had irregular periods and have not had a positive ovulation test in months (though I've already birthed one child without assistance). My doctor prescribed Clomid, and this month is my first round. I'm on day 21 of my cycle, no positive ovulation and starting to spot a little. Is it too late this month to ovulate? Getting worried it won't happen at all. :(