losing piece of mucus plug not normal?

so last week Thursday I lost a piece of what I'm assuming was my mucus plus, I'm 18 weeks and most people here said it regenerates and that its normal. my mom said in all her four pregnancies that's never happened to her till she was close to giving birth. its Sunday so I called my after hours OBGYN office, they pages a doctor about it. been waiting two hours for a call back. I don't have cramps or pain or blood, so I wasn't worried at first, and it didn't happen again. someone said it. could also be weird discharge because of recent inter course, but it was indeed thick and stretchy and odd looking, I don't know what to think