My sweet baby going mean

 My lovely sweet Jack was the most loving and gentle child in the world and has been like this since birth.He has always been just a perfect angel but 3 weeks ago it all changed!Three weeks ago I saw my son throw a tantrum,I thought he was in pain or something because I had never seen him roll around screaming and kicking.My mom was with me when he was doing this and she told me it was nothing more then a classic tantrum.Well, I ignored him while he did this and I went about my life like Usual.
 Three weeks have passed and now my son is completely different then that loving angel he once was,he is 2 1/2 on Feb. 8th and for over two years he has  just been so easy to take care of but it seems that is all over now.
 My son has been biting,scratching,throwing tantrums in public and just being a total monster!I feel so crazy! I have put him in at least 10 time outs today for hitting and scratching.I have yelled and now my throat is sore and my nerves are on edge but my son seems to be a real cool number.
 I have read all the books,I have seen and spoken with many parents but I just never thought this would happen with Jack. I just was not prepared for this.He was slow to get caught up to the terrible twos.
 Any advice?