"It made me feel really bad"

In October 2016 I started developing serious headache and loss of balance. I've seen My GP a few times. I've done 2 blood test testing for various things such as thyroid etc but everything came back normal. Shortly all of a sudden I started gaining weight, like 18 Kg. I stopped playing sports as the headaches and the weight gain wouldn't let me perform. After a few weeks I started having problem with my breathing and I couldn't take a deep breath. I've seen my GP and tested for iron deficiency and vitamin B12. The results came back and my vitamin b12 levels were low 17 and Folate serum was below the normal level as well. The doctor ordered me to have 6 injections over 2 weeks. I had my injections done and in the meantime I changed GP as I changed address. After more than a month I developed really bad weakness, muscular pains, numbness in my legs, problem with my breathing and the usual headaches. I rang NHS 111 as I thought going to the A&E would be a waste of time, they didn't see me as they said they couldn't do much. I went to see my new GP, which told me off for calling NHS 111 as soon as I came in. He also didn't seem to believe me saying that I didn't have a vitamin B12 deficiency( blood test results proved otherwise) and he kept insisting that I was depressed which I am not. He asked for my profession (which I found out of context) and he treated me like an idiot. He just gave me some papers for some blood tests and told me not to call NHS 111 or ambulances as it wouldn't help anyone. I never called an ambulance but he instisted on that. It made me feel really bad, especially because I am a young adult who was healthy and active before this problem and he put me down a little and made me feel hopeless. I wish I could afford private healthcare as the NHS GP's so far treated me like as a liar.