It is highly recommended to complete the full three-dose course of your medication (goserelin) as prescribed. This therapy works by consistently suppressing estrogen levels to shrink endometriosis tissue and relieve pain. Stopping after two doses may prevent the treatment from being fully effective, and your symptoms could return sooner. The side effects you are experiencing, such as insomnia, headaches, and nausea, are common as your body adapts to lower estrogen. Please do not stop your treatment abruptly. Instead, contact your doctor. They can suggest ways to manage these side effects, such as low-dose 'add-back' therapy, to help you comfortably complete your final dose.