What are some signs of preterm labor

Ugh worried about preterm labor. I keep having a feeling baby is coming and even having dreams about it. I’m only 31 weeks and my first came at 37 weeks. I’ve been having Braxton Hicks for two months. But some light cramping the past few days. Also I’ve been losing bits of my mucus plug. Today I have been having bad back pain, cramps, and I lost a huge glob of my mucus plug. With my first I lost this big of a piece and then a few days later had my bloody show and went into labor. I’ve also had some extreme pelvic pressure. Should I call on Monday and see what they say? Or just wait it out