Hello, So I Found Out That I Have Anemia Which

Hello, so I found out that I have anemia which my hemoglobin levels are beyond low. Some of the symptoms that I have are numerous episodes of me passing out, fatigue, dizziness, headaches, off balance, nausea, vomiting, and no feeling in my legs. A couple of days ago I experienced lower back and stomach pain on the right side. It hurts to lie down, sit down, to cough, or even touch it. It also affects my ability to walk. Do you know what is causing me to feel this way?