Always thirsty, tired, headaches - should i get checked for diabetes?

Yes: These symptoms could be from other things as well but diabetes is one of them. You should get it checked. Blood draw is all you need.

Yes, you are right: High sugars in blood mean that the body is unable to use glucose. So, body and brain are starving for glucose. The body in response attempts to use glucose via other methods. Byproduct such as ketones build up. These can lead to a diabetic coma. Some people get headaches or nausea or sleepy or blurry vision or almost any symptom. The thirst could be a symptom. Please see a physician.

Yes: Yes you should get checked for diabetes, more importantly you should get checked, meaning go to the doctor. You state you "always" - what are you waiting for? Do not wait, make an appointment asap.