It is quite possible the formula is upsetting him, it takes their bodies much longer to digest it and his system would be churning and working harder to do that. Giving your baby a bottle or solids to help them sleep through the night, especially at such a young age is not a good idea. Some people do find it helps with sleeping, but only because of what its doing to their system. As adults things process quickly in a matter of hours, but for babies its much slower. Some babies will try and sleep it off and others will get upset. Breastmilk contains 100% of their nutritional needs until around 6 months. You might also like to read this article. I'd also invest in a copy of 'The Wonder Weeks' which explains the developmental milestones, tells you when they are and the unsettled periods and things you can do to help.