Thanks for the query to H.C.M. Forum.
I would come up with these possibilities , these includes .
1 False labor pain
, as you are complaining that pain is in the back and radiating in the lower abdomen with downwards .This is a clear indication that this may be false labor pain.Diagnosis can be confirmed by physical as well clinical examination by gynecologist .
2 The 2nd possibility may be urinary tract infection
. Diagnosis can be confirmed by culture of urine.
3 Spine pain , lumbo-sacral vertebrae pain . Diagnosis can be confirmed by C T scan.
In my opinion consult an obst and get his opinion .