Tmi..back pain 26 weeks

Yesterday all day I had the worst back pain, I've been on iron tablets and haven't been able to go to the toilet. I was practically limping before I got to bed, and was worried as I had been lifting my toddler. I suddenly felt nauseus and spent the whole night with diarrhoea and nausea. I woke up with no back pain and feeling almost back to myself. Is this normal or should I be worried. It's happened before with nausea but not the cramps/back pain/diarrheoa too.