Hii , 
Welcome To HCM & Thanks For Asking Your Query Here 
it's common to have lower 
back pain After a 
miscarriage , pain is normally mild to moderate, but if you are feeling constant severe lower back pain u should consult With ur OB/Gyn
you can take Over the counter Painkillers like 
ibuprofen to relieve ur symptoms but It is better to use simple 
home remedies to alleviate the pain
Given below are a few instructions for you 
-Get an adequate amount of sleep and rest ,Perform a few back-strengthening exercises that can get rid of the tension in the lower back area, Soothe the muscles in the back, by soaking in a hot bathtub at least once, or even twice a day.
-Place a big filled with hot water or a 
heating pad on the lower back area. Alternating between hot and cold therapy is also quite beneficial.
finally i would strongly suggest you to see ur Gynecologist to rule out any other underlying medical condition 
I hope it help 
Thanks & Get well Soon