Mucus plug

Hi everyone.. I’m new to the whole pregnancy thing.. and I’m 33 weeks, but she’s measuring 2-3 weeks ahead but no ones explained anything to me about it so I have a couple questions,

1. Is it the mucus plug

2. Do I need to let my midwife know right away or do I wait for my appointment to let her know

3. How long before I start showing signs of labor once I lose it?