Sounds like the toxins from mercury and root canal are affecting your entire sinus regions and creating headaches nad pain behind the eyes, pressure etc. I think mercury combines with the toxins from root canals (and cavitations), creating some very nasty toxicity.

You can definitely take algin now! You can take it now, during and after amalgam removal indefinitely if you want. It should help bind up some of these toxins.

Look at diet too. So many people do not think about their diet and don't realise that diet plays a huge role. Usually mercury toxic people have got to go on a strict diet in order for their gut and body to have a chance to heal and elmiinate toxins easier. This means no sugar, no yeast and no gluten grains. All those things contribute to the toxicity and can overload the already burdened liver and gut. It can help alot in some cases.

I have no choice, I'm so ill, I cannot eat any sugar at all, or even fruit. candida is a yeast infection that usually happens in mercury toxic people and eating any sugars feeds this and contributes to the toxicity of mercury, causing further unecessary suffering.

I hope this helps a little.