Preterm labor signs

I’m experiencing lower back pain and pelvic pressure. I’ve read that these are symptoms of preterm labor, and you should call with ANY symptoms of preterm labor. However, I am only having normal, irregular BH - not real contractions. I also know that pelvic pressure and lower back pain can just be pregnancy symptoms. At what point would you call your doctor? If you got real contractions? Your water broke? Pelvic pressure / back pain intensified and continued to the next day? I don’t want to be absurd and call over a normal pregnancy symptom, but I also don’t want to ignore symptoms that could be preterm labor.