as far as I know , backache is normal in early pregancy , but given your history it is better to see a doctor as soon as you can to make sure everything is .Take care and I hope everything goes great for you!!!
Hey, İve just learned im pregnant and i have been asking the same question. İ have back ache. İve had a previous miscarriage and it started with back ache but i think (well im hoping) that it might be all in my head because so scared that i will lose this baby. So my body is giving me signs which make me more unrelaxed. İ dont know but we can be here for each other if u want because im just a couple of days behind you.
You could have a blood clotting disorder that is causing you to miscarry. Baby aspirin should help, perhaps along with Prometrium.
Other than that it's a waiting game. Backache does not always signify a problem but because of your history I'd definitely call the doctor and start getting those betas done.