I have seen a GP, but he explains that there could be something wrong with my eyes, causing the headaches which leads to nausea, but my optometrist says my eyes is in good condition. I have been experiencing nausea, permanent headaches, a weird taste in my mouth, like a hangover, but I don't drink alcohol or coffee. I was taking Roaccutane for 6 months, but haven't been taking for 4 months now. I donated blood about 3 months ago, the similar period that I started feeling this way. What can be wrong with me?