Levels gone crazy :(

I will admit i have been naughty over the christmas period and gone with the flow (I know I shouldn't, but lack of willpower and influenced by family) I havent checked my levels either, but last night I checked them and OMG they were 22.5! this morning they were 9.0 so thought i would knuckle down and try and get on track again. After a cup of tea, 1 sweetner and semi skimmed milk my levels spiked to 14.5 I ate my breakfast, 1 sausage, 2 fried tomatoes, 3 fried mushrooms with stilton on them, 3 rashers of bacon and an egg. Checked levels 2 hours after breakfast and a cup of coffee with 1 sweetener and milk and they are back down to 6.0. What on earth could have caused a spike of 5.5 with only a cup of tea?