Hi bazaboy.I'm so sorry your boy has been through such a terrible time with his snakes - hopefully now you're in contact with the excellent advice this forum gives you will have a better time with your current snake.
Please can you tell us what temperature the heatmat has been running at and, as Bleckecho asked, what are you measuring the temperature with? As well as being attached to a thermostat the maintain the correct temperature by turning the mat on and off, you also really really need to use a digital thermometer with a probe so you can accurately measure the temps at all times.
The digital thermometers I have only cost £2.50 from Ebay (here's the link http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=230420653810) but they mean I can quickly glance at the temps every time I pass my snakes homes which ensures their safety. One day Twilight moved his thermostat probe off of his heatmat and the temp climbed up very quickly. Being able to spot the temp change meant I could rectify this immediately before he was harmed. Some guys on this forum have run experiments to see how hot a heatmat will get if not attached to a thermostat and it was incredibly high - definitely hot enough to cook a snake.
In the past when someone has had a faulty thermostat they have been told to turn off the heatmat as it is much safer for the snake to have no heat for a few days than an unregulated mat which could kill it. If you have no thermostat (and no digital thermometer too?) then I think you would be best doing this and just ensuring the snake's faun is in a room which has heating then get to a reptile shop asap to get the necessary kit.
Please correct me guys if this is wrong. Good luck bazaboy
08 male Carolina Corn ‘Saracen’ 09 male Anery Corn ‘Twilight’ 08 male Rankins Dragon ‘Keydo’