Baby mood change at 2 months?

So around two months my son has had a shift in his mood and responses to things. He is more irritable then before and sleeping quite a bit. Such as you can't take the bottle from him or he cries (we take it out because he drinks it to fast) or when we try and burp him he cries. He cries now when we lay him down to change his diaper and just in general seems to be different demeanor then he used to have... did i do something wrong? it's just seems so sudden to me it's just making me think I did something making me a bad mom... I am a first time mom so please be kind.