Babysitting 3 month year old help?

Today i babysat a 3 month year old boy. it went well @ first but than he started crying and screaming. I Changed his diaper, Tried feeding him, walked&bounced him around the house, i tried EVERYTHING. After i gave him his pacifier he calmed down a little bit but i had to CONSTANTLY entertain him and squeak a toy infront of his face non stop. I am so nervous for the next time i visit him and i am scared he will do the same thing. Any tips?! please?! By the way i am 14.