Harmless lower back pain, Braxton Hicks or preterm labor contractions?

I've had lower back pain for a few days now. It doesn't come in waves but is there 24/7. I've had a few painless Braxton Hicks -contractions but it was before the back pain occured. I've also felt slight period-pain-like discomfort in my lower abdomen, and the backpain makes my thighs ache.

This is my first pregnancy so I've got no idea what early contractions or harmless but slightly painful Braxton Hicks -contractions feel like. Is this contraction pain even if I can't feel my uterus cramping or my stomach hardening?

I called the nurse today and she said she thinks it's just ligament and growing pains but if it gets stronger and rest doesn't help, I should call her again next week. Now I'm getting stressed over the fact that on the phone I forgot to mention I can feel the pain / ache in my thighs as well, and that these could be the signs of a preterm labor and I should be in the ER already. 😂

I hate being this paranoid but I just worry so much! Any advice if I should just call her again tomorrow, wait until next week's appointment or visit the ER today?