It looks like your old backache
has recurred due to the laxity of the ligaments that happens during pregnancy
as well as the stretching effect of the enlarging abdomen on the back muscles. The symptoms relate to a nerve
compression. You need to see an orthopedic for a proper diagnosis and management as if left uncorrected now, this is going to get worse later on in the pregnancy causing unnecessary trouble. You may need physiotherapy
in as much as your pregnancy allows. Meanwhile, you may take pain killers and local applications after consulting your obstetrician. Take care.