This will depend on how it switches on and off and how you feel when you dont feel depressed and when you do.
It could be the following:
1) The come down from Alcohol or/and drugs can cause dysphoria which feels like a depressive illness and is very intense
2)If you feel overly happy or active and hyper when you are off the depression feelings you could have bipolar disorder which is a type of depression that causes two extemes of feelings and moods and can be controlled through medication
3) It could be that you sometimes can become unhappy for a time and then something will make you happy again and so there will be nothing to worry about and its normal - normal moods.
4) You could have a very mild form of depression which causes very mild depression you are morely likely to have more days where the depression feelings subside a bit more - and it can be a continuous mild low mood - its called dysphora or dysphoric Disorder.