I am taking betolvex and theregran pills for almost now 3 years because I had my severe eye nerve pains and low haemoglobin...What should I do?

Get evaluated. Anemia can be due to many causes. B12 and iron deficiency are 2 causes. A blood count should be checked to see if the anemia has responded to these supplements.
Eye pain and anemia. Your description sounds serious but there is not enough information to know what is aiding your issues. You should see a regular and an eye doctor for further evaluation.