melatonin for toddlers??

my son is 19 months and he wakes up at 230 and 530 every day. he's shattered by 10am and goes to sleep for an hour or so,but that's the only nap he has, unless we're a long journey in the car.

I'm pregnant again and it's killing me never getting a sleep. I know it's part of having a baby, but I though by this stage he'd be sleeping.

I've came across melatonin drop to aid sleep, but nonw of my friends or family have used it so looking for some advice from people that have??

thanks