Hi Matty,
If you are in the UK and want to get tested today, Lloyds Pharmacy have a free diabetes testing service where they will do a Blood Glucose test on you and then let you know whether or not you have diabetes. If you do have diabetes, it is likely you will need to contact your emergency doctors service, the phone number should be given on the answerphone of your GP's surgery, or you could go to A&E depending on where you live.
If its not diabetes, it still sounds like something serious

)
Sean