As a long time sufferer of depression, I would say if you are feeling down for no reason, it is probably more of an indication that something is going on with your body. Sometime it is not depression, but maybe something like thyroid, or hormones. Some people are also effected be the change in seasons/weather. It's called
SAD .I'd just go in and have a chat with your doctor. Mild deppression can be easily treated and you don't even always have to take meds.
Hope you get to feeling better.