tired and dizzy

My parents have gone away on holiday and I had some friends round on Saturday night. On sunday morning I woke up and felt ok. I had some friends round again to watch the football. At around 6:00pm i felt really tired which is very strange for me. I had had not much to eat that day just crisps and a lot of fizzy drinks. I thought it might be something to do with lack of energy from not eating. Anyway I went to bed at 6 and awoke at 3 in the morning and got up and felt quite dizzy and unbalanced. Once I have walked round for a bit it seems to improve but I just would like to know what it could be. I also feel very tired, as if I could sleep for ages and not feel the need to get up. Its strange as this only happened last night and i have had nothing like this before.