I'm sorry to hear that you've been experiencing headaches, eye pain, weakness, and occasional abdominal pain. These symptoms can be caused by a variety of factors, including changes in diet, nutritional imbalances, or emotional health such as depression.

Changing your diet to gain weight might affect your body in different ways, especially if the new diet lacks certain nutrients or includes foods that your body is not used to. This could potentially contribute to some of your symptoms like abdominal pain or weakness.

However, symptoms like persistent headaches, eye pain, and weakness should be carefully evaluated to rule out other underlying conditions. Depression can also manifest with physical symptoms such as headaches and weakness, but it is important to have a thorough assessment to understand the cause.

Given the complexity and persistence of your symptoms, I strongly recommend consulting a doctor, preferably a neurologist or a general physician, who can perform a detailed evaluation. They may suggest appropriate tests or refer you to a mental health specialist if depression is suspected.

If your symptoms worsen or you experience new symptoms like vision changes, severe abdominal pain, or significant weakness, seek medical attention promptly.To narrow down potential causes, we will need some more information.Please tell me your age and gender.