33 weeks pregnant preterm labor

Hi, I am 33 weeks 2 days with a Babygirl and since 4am I have had on and off cramps (stomach tightness) with lower back pain. Thankfully I had my obgyn appt today but all he did was do an ultrasound and said everything was ok. Did not check to see if anything was opening since he said in the ultrasound everything looked closed (over the stomach ultrasound) he said to take it easy, lay down drink water and take ibuprofen his words (take 4) which I’m pretty sure it’s not recommended. I still have cramps and back pain (6:33pm) I don’t know if I should wait it out until tomorrow to see how I feel or go to the er. Any advice would be appreciated.