Firstly having worked in HR and now working as a professional person in the criminal justice system I have recently had experience of bullying by my boss too. You are covered under the DDA which means that you are entitled to more sickness than other members of staff, the company does not have to discount them but they should be flexible with regards to time off. Try not to get signed off sick though unecessarily (if you are depressed but the GP calls it otherwise) because this will affect your work and they can start proceedings if they feel you cannot do your job. It comes under competancy in your role.
When I was first diagnosed at 34 (Type 2) I had actually had diabetes for at least 2 years prior feeling like c**p all the time and picking up infections here there and everywhere. I was in shock and denial and probably still am (now 37). Anti depressants dont really help, I was prescribed amitryptiline but try not to take them. I started on oral medication and suffered extremely high blood sugar all the time, got admitted to hospital several times and again felt like c**p all whilst working 3 jobs. In the end because I was always feeling ill my boss started making things difficult for me when I asked for an adjustment in my job. I got referred to occupational health - best thing that happened to me as OH came back and agreed with the adjustment, mentioned that I needed extra sick days and flexibility in my role and quoted the new Equality Act. I haven't had any problems with my boss since, in fact he has been quite understanding. I still feel like c**p but just get on with it, I look at it as im alive and have all my arms and legs which in reality others who suffer from diabetes don't, have you read how many people get ampuations on their limbs!
I know its hard but go with the flow, ask to see a diabetes specialist nurse not the GP as they deal with diabetes on a day to day basis and will sit and chat with you about anything thats bothering you - mine are fantastic!
I inject now, not insulin but a drug called Victoza. Ive lost some weight and my Blood sugar is down to between 9 & 12mmol which I feel is great progress for me. I have high blood pressure, bladder problems, arthritis and inflammatory joints and other health problems all caused by diabetes and being overweight. If I let all of these get on top of me, I probably would give up and die - I considered that too, I think we have all been there.
Just know that there are others out there just like you so don't feel to disheartened, try and find a relaxation technique to help with the stress, swimming or yoga is great, but remember try to get to see the specialist nurse in your surgery as they will help you. I had a needle phobia and cried like a baby when I was told I had to inject, now it takes me two seconds and I think nothing of it thanks to my special nurse's technique.
I found it was also useful to tell my colleagues I had diabetes as they were there to support me when I was having a bad day which is normally quite frequent, they are all very understanding.
Good luck and keep your chin up!