welcome to HCM,
as u have mentioned about your problem, this backache
or LBA is due to pregnancy
normally after pregnancy ur back muscles get weak and after that u need to strengthen ur back muscle along with abdominal muscles which keeps your back fit and fine.pain free..
now coming to the point.for ur reduced disk space u need to do a MRI scan to find out the nerve involvement in detail.
now u need to consult a physiotherapist to assess ur pain and prescribe u the proper exercises to avoid pain..
u can have normal diet but avoid constipation
which agrevates the back pain
you can conceive but it can increase ur back pain.. so better go for proper exercises and then u can conceive next time..
hope this piece of advice will be helpfull for u..