How long have you been taking the medication?
What is your height and weight?
How is the rest of your health, do you take any medication for other problems?
Being a patient with diabetes then we do like to see your blood pressure down a bit more.
You are overweight for your height so focusing on losing weight through increased exercise is essential. This will also help other problems as weight loss will also reduce blood pressure but I can appreciate with RA than movement may be difficult and painful. Swimming is a good place to start as this helps support the joints.
You have only been on the cozaar a couple of weeks so I would give it more time. You should also cut your salt intake down to below 6g daily as this has a direct effect on blood pressure.
If there is no response to the medication then you need to be under the care of a cardiovascular or endocrine doctor.