I had a very small amount come out when I was about 29weeks - looked like a blob of green snot about the size of a kidney bean. midwife said not to worry unless I continued to lose more or have other symptoms as it can regenerate itself.
How much was 'a lot?' Was it tinged with blood at all? Do you have any cramping etc?
If your doing ok otherwise I would just take it easy - lots of stuff online says it doesn't mean that labour is imminent, it can still be weeks before, however if it was your complete mucous plug then you are more susceptible to infection up there so no doing the deed/having a bath etc until you've spoken to a doctor or your midwife
Xxx