Sleeping problem with 13 month old?

I'm losing my mind, before he stayed at my MILs he slept fine, he would wake maybe once or twice a night and would settle as soon as he was given his dummy (pacifier) now he is waking around the same amount but he is very difficult to settle, I have to stay in his room patting the mattress for him to sleep, I have to pick him up to give him his dummy and I am awake in his room doing this from 3 am every morning, he just wont go back to sleep after this time even though he is absolutely exhausted! is there anything I can do to help him sleep?