Daughter won't sleep!!

Not so long ago we had a problem with our daughter not sleeping. She would purposely wee or poo in her bed to sleep with us. She wouldn't sleep until 4am some times. We solved this problem by getting her a night light, putting her to bed at 8 and reading her a story not letting her have a film on to sleep to. She was doing amazing going to sleep early and getting up at a reasonable time instead of sleeping all day. We needed to do this quickly as she's 4 and starts full time school this September. But now! It's all gone tits up! We do the same routine, glass of milk, brush her teeth, toilet, pjs and story in bed. But instead of going straight to sleep after the story like before she's getting out of bed putting on clothes getting toys and banging on the wall. I go in and tell her if she does it again the light goes off but she will laugh it off and say I want the light off, so I turn it off. Yet she's still staying up untill between 10-1 some nights. She's not even waking up late she's getting up early, I'm 40+4 weeks pregnant and this is killing me and my partner! Anyone have any tips or ideas on what I can do?!!! Feeling helpless as she's going to be way to tired for school specially with a new baby!