Should I talk to my doctor if I've been feeling down?

I don't think I'm depressed (or if I am it's only mild) but lately I've been felling down from time to time and I've had three episodes where I cried for no reason and just felt really sad. The rest of the time though I'm completely fine. It's not affecting my daily actives or anything like that although I have noticed that I'm a little less motivated about things I used to care about a lot. My mum thinks I need to talk to my doctor about it but I'm not sure. What would my doctor do anyway? Is there any point talking to her? By the way I'm a girl and I'm 17.