Thanks for writing.
The symptoms you have mentioned can be seen with a urinary tract infection
(UTI) which is very common in pregnancy
. Lower abdomen pain with back ache, dark urine, burning in urination with increased frequency can all be seen in UTI.
The other possibility can be a genital infection
which present with discharge, pain abdomen, backache
You need a visit a gynecologist for an internal examination which would rule out genital infection. Also urine microscopic and culture test is required to rule out UTI.
In the mean time, take plenty of fluids. Avoid intercourse and maintain hygiene.