You have one specific disease- diabetes. The medication you are on for diabetes needs to be modified. Metformin should be included in the regimen and any inclusion of any other medication for your diabetes should be in accordance with your glycosylated 
haemoglobin (HBA1c) level. Your daily calorie requirement should be specified in accordance with your 
body mass index (BMI) and your lifestyle ( sedentary, moderate or heavy worker). Regular exercise, monitoring of blood pressure and 
lipid profile and screening for urine 
microalbumin are needed.
Secondly, you have arthritis. You havenot specified the type. But you are on DMARD 
Sulfasalazine. So, you might have 
Rheumatoid Arthritis. But I need definite confirmation regarding the same which can be done using further investigation.  If, unfortunately, at all you have RA you must know that RA can affect several organ systems of your body apart from your joints. As you have diabetes alongside, your kidneys need to be monitored closely and infection needs to be prevented .
My advice will be -
Treatment under supervision of an endocrinologist/ 
diabetologist and Rheumatolgist with diet advice from a therapeutic nutrition specialist.
However, a good clinician who has specialized in internal medicine can also solve your problems if you don't have access to the above mentioned specialists.