Helth Cover

So I’ve bought a car and got my driving test in one week but been sent a letter from the DVLA stating when I receive my driving licence, it will only be valid for 3 years. After this amount of time I then have to reapply where they can check the medical records again. But because of this my insurance started at £1,400 a year but has now gone up to £2,800!! Why am i being charged this much more? Has anyone else got a similar problem. I feel like not even bothering to take my test now until i can afford it and count my losses