My vitamin d level was low enough that my doctorprescribed 50000 iud a week, could this contribute to depression?

Unlikely : Some studies suggest low vit d may have an implication in depression. When taken at high doses on a regular basis, hypervitaminosis d may ensue. This can cause psychiatric symptoms (eg irritability) commonly accompanied by GI symptoms. Hi vit d can cause hi ca which in turn can cause "psychiatric overtones": depression, anxiety, insomnia, altered cognition & mental status & many other bad things.