I completely understand you saying you don't want to let your diabetes take over your life, and I absolutely agree, but you also have to accept that whether you like it or not, diabetes DOES change things. We have to be far more mindful of what we do than we did before we were diagnosed, and things like shift work - which is unhealthy for anybody over the long term - doesn't help matters. You have to consider whether your lifestyle is part of the cause of your problems.
I appreciate and am sensitive to the fact that you're adjusting to a new way of life after having recently been diagnosed, and I understand that you do of course enjoy your job but you know the side effects of poorly managed diabetes, you have to seriously consider whether you really can continue in the job you're in. Walking away from something you enjoy is hard but there's nothing to say you couldn't find another job you enjoy just as much, but one in which you are better able to manage your diabetes.
The human body is extremely sensitive and it doesn't take much to disrupt its rhythm and throw you back to square one. It doesn't sound like you are making much progress and it seems that your current job is hindering your ability to manage your diabetes, rather than supporting it.
Alternatively, if you really do not want to leave your job then is it possible to talk to your employers to see if they could keep you on day shifts for the time being, just while you get yourself sorted out, and then look to introduce the shifts gradually?
Whether you like it or not, diabetes is now a part of your life. You're absolutely right that you cannot let it rule your life, but you do still have to take its impact and management into consideration and unfortunately that may sometimes mean we have to make decisions we don't want to make.
Personally, I wouldn't hesitate in looking for another job if it was impacting my health, and in fact I've left jobs in the past for that very reason, and would do so again. But please, if you don't want to leave, at least work with your employer to see if they can be more accommodating for you. As your employer they have a duty to ensure your health and safety.