Help im Exhausted😴

My son is 1, and i cannot get him to sleep through the night. He was doing great only waking up 1 time around 6 am. But now i feel like its every hour or so. Im 4 months pregnant and it is started to take a toll on me. 😴 my mom will take him for a day over the weekend every other weekend. sometimes. but because he doesnt sleep good she doesnt want to no more because it makes her tired & i understand. How can i get him to sleep more at night?

*i dont need any ugly ass comments about my kids being so close in age*