Question about low ferritin level?

I just found out my iron level is 20 and my ferritin level is only 3. Now I know why I'm so weak and tired all the time. I have other weird symptoms too, like bad dizzy spells, burning tongue, sores on the sides of my mouth. Does anyone else have any of these symptoms if your ferritin is really low? I also have to have a colonoscopy and I'm kind of scared about it. Anyone that has experienced any of this, can you please share with me?