I would get checked out! I was having the same thing at 34 weeks and turned out I was 4cm and 75% effaced! Started with back pain then menstrual cramps
I'm having the same thing, plus gas pain. I've been in labor before, (this is my second baby), so for me, it's safe to say that I think I'm fine. It's not comfortable though, especially the cramping. The lower back pain hurts even while laying down. I have a doctor appointment on the 10th so I guess I'll find out for sure. I'm only 23 weeks 3 days.
Two nights ago I had to be taken to emergency L&D because I had the same problems! Horrible cramping and severe back pain, especially on my right side. I was in tears. Turns out I was having contractions every 2 minutes and was 1cm dilated. They kept me overnight to stop the contractions, I got some pain meds and now I'm home on bed rest and I'm only 24 weeks! Better safe than sorry. Get it checked out mama.