Hello dear,
I understand your concern.
In my opinion the pain in lower back might be due to various causes like:-
1)
Muscular pain.
2)Pregnancy related like any suspicion of
miscarriage but here the pain is associated with abdominal cramps with or without spotting.
3)
Constipation causing low back ache.
4)Any
renal stones - Here there might be urinary symptoms like burning or any.
So all the above causes should be evaluated.
I suggest you to see a doctor and get any necessary investigations like ultrasound,complete urine examination done.
Nothing to worry.
As per your information the
low back pain appears mostly due to muscular pain as you don't have any associated symptoms as I described above and it has been since 5 weeks of pregnancy.
But it needs to be confirmed after physical examination and necessary investigations.
So kindly consult a doctor.
Avoid physical strain and intercourse.
Take good rest.
Hope this helps.
Best regards...Dr.Srilatha