Back pain

I had some horrible back pain last week due to lifting my client (42lb) a lot more than usual last Tuesday. I got a heating pad and tried as much as possible to not lift my client the rest of the week. I had a long weekend also with work. I switched to night shift on Sunday so I won't have to lift more than 1-2 times at the very beginning of my shift. Ended up being cancelled Monday night due to the snowstorm. By Tuesday i was feeling much better and didn't need the heating pad anymore. Tonight, my daughter (40lb) was acting up and wouldn't get dressed for bed so I ended up picking her up and she was wailing around and it killed my back. I'm so mad that's it's hurting so bad now. Luckily I don't have to constantly be up and moving for work overnight but I'm having trouble getting comfortable. In top of that, now I'm cramping more than my usual (no pattern or anything though). Any advice regarding trying to get comfortable while I'm at work? Do you think I need to call the doctor about the cramping?