I know the feeling I have had the same problems in the past. But let the employer know before you start the job...and go from there. Hope this could help you in the future

Have you gotten your back problems looked at and know what they are? It is true that companies will expect you to be working and if you are calling out too much, they'll need to find someone to replace you. But maybe if they know in advance what's going on, they can work with you.