I need some opinions, I am calling my Dr. So this morning I wiped and there was about a quarter…

I need some opinions, I am calling my Dr. So this morning I wiped and there was about a quarter sized of what looked like mucus plug, it was yellowish. I'm a little crampy but nothing major. This hasn't been the first time that this has happened but it was tiny amounts. I'm 20 weeks, what could be causing this and is it normal