what does it mean if your stomach is hard and tight

Any pain?

If it comes with pain could be a sign of labor coming

Braxton hicks contractions most likely. Your body is preparing for labor down the road. I get them a lot, even now after cleaning the house.

but my mucus plug fell out 4 days ago

my lower pelvic area hurts a little

I'm 34 weeks 4 days

I also have diabetes