Hysterical isn't the word!

Well, something happened almost overnight, my generally chilled well behaved (as much as you can expect anyway) two years and 3months old toddler has turned into a little person that I hardly recognise??? His behaviour is unreal, if his demands are not met instantly all hell breaks loose, sobbing, throwing himself on the floor, screaming till he's almost sick and will only be consoled by me giving him lots of cuddles to calm him down. I don't know whats happened, I mean I accept that they will go through phases but its as if some awful life event has happened (it has'nt) and he sobs at the slightist thing? Please tell me I'm not alone in this, I'm starting to feel like I'm really doing something awfully wrong for him to be so emotional about everything? He gets lots of positive attn from both me and my husband all the time, playing and interacting plus we go out and do things regularly, different music and football classes etc HELP? Jude