Im feeling a bit off today

First off im 37+3 with my first baby. I worked an overnight shift last night. I got to work feeling just fine. Then a hour later i lost all energy. My lower back started to ache and i got nauseous. My BH became more intense also. Kind of crampy id say. But not painful. I almost feel like im getting sick but im not? Ive been off work for 3 hours now and my lower back still hurts and i just feel like crap. Is my body just preparing or could i be starting labour? I just feel so weird and it was out of no where. Ive been dialated 1 cm for the last two weeks, which last tuesday my doctor said i was still at 1 cm. So no progression there but anything can happen.