My 3mo doesnt sleep through the night

My 3 month old used to sleep 7-8 hours at night but now he is back to waking up 3 times at night. I am very tired. I exclusively pump for my baby and He eats like 1100 ml a day so he is not hungry. What can I do to make him sleep better? ( he also pushes the paci out, I have to trick him with a bottle first)