Welcome to HCM.
You are carrying 8wks of pregnancy and presents with back pain and mild brownish spotting.
It may be due to early implantational bleeding or THREATENED type of MISCARRIAGE
which is recoverable mostly.
First of all,you do a fresh USG for FPP and check for fetal well being, heart status or any abnormality.
To prevent miscarriage,it is ideal to take Natural micronised progesterone like (Naturogest
or Trugest or SUSTEN or Others) along with Folic acid
supplements (+/-)uterine relaxant and use of anti fibrinolytics.As progesterone deficiency
is an important cause of early wk abortion.You need periodically check up for fetal status and consult with your doctor.
Also avoid heavy work,long journey and go for complete bed rest. Back pain is quite common in early pregnancy and it can be overcomed by application of local muscle relaxant
Be well and happy journey for future pregnancy.