I bent down and felt faint and saw dark spots?

Vasovagal: You are either dehydrated or likely experienced a vasovagal episode. If this keeps happening other less likely etiologies should be considered such as hypertrophic cardiomyopathy etc.

Any medications?: Generally blood pressure medications can cause lightheadedness with sudden change in posture such as bending and straightening up. This can also cause blurred vision and spots. If it happens repeatedly review your medications with your doctor and check blood pressure in sitting and standing posture. If not on any meds you need a thorough evaluation.