Hi Samridhi baby is just 1.5 months and sleeping at a stretch is not possible. They sleep less in night and more in day till their routine gets settled, they are new to this world. It takes 2 years to sleep throughout the night. You can start setting a routine take him for a walk, give him massage, give towel bath, wear fresh clothes and keep the room dim lighted after 7 pm. Breastfeed him in lying down position, he will also sleep and you will also get some rest. But he will definitely get up often for milk so please breastfeed. Its definitely difficult phase, its been 17 months since i slept at strech for 4 hrs also. So sleep whenever he is sleeping. You will get used to it.