I just got my lab results back and my hemoglobin is 90 g/l. i'm not bleeding anywhere. how serious is this?

Extremely: Every anemia is a warning. You need to get with your phyiscian and not stop getting evaluated until the cause of your anemia is found. Whatever is causing this is a greater danger to you than the anemia itself. I'm very glad you have found sobriety and trust it has been a blessing. If your primary care physician can't find the cause, get with a specialist. Best wishes.