How do I know if I'm depressed or just lazy or unmotivated?

Depression comes with many other symptoms. You may want to look them up online to see if you fit with any others.

Asking that question in itself is a good sign. Depression drains all your energy and nags at you about all the things you "should have done" at the same time. If you feel as though you cannot "pull yourself together", I take that as a sign of depression rather than laziness.

You might consider skipping the self-diagnosis and focusing on the symptom -- the lack of motivation. Try to focus on things that matter to you. Start small. Sometimes we just need to find the right environment, or people, or goals to feel motivated. If you work hard to stay active and healthy and still find yourself lacking motivation, then you might want to look into the etiology -- the cause. Some research into CBT (Cognitive Behavioral Therapy) techniques might be a good place to start. Many of these techniques are straightforward, easy to apply on your own, and have immediate impact on our thoughts and behavior.

Usually you'll feel guilty about being lazy when you're depressed. If you were just lazy you probably wouldn't care which you obviously do since you're asking for advice.

The simple answer is: because your depression is telling you that you're a lazy person. Even though my depression negatively affects my daily functioning and I have been professionally diagnosed (though I self-diagnosed first, and that is also valid), I still have days where I'm convinced that I'm just incredibly lazy and have tricked myself and others into thinking it's depression. This happens almost weekly, and the reason is that when you're depressed, you think that there is something fundamentally wrong with who you are as a person, even though that isn't true.

It is a different feeling to be unmotivated when you're lazy vs depressed. You feel empty when depressed and do not want to do anything. Being just lazy would equal you wanting to do something but favoring doing nothing.

Well for me I know I'm lazy but I still love to practice my music and competitive swimming but when I'm unmotivated thanks to depression I loose intrest in things I love to do normally

Just think about before: were you a lazy person or you enjoyed doing things? You can see if you are always lacking of energy and if you have to sleep a lot to recover from your day. You could consult a doctor, he will be able to help you find if you are depressed or not.

It just feels different. When you're depressed, you don't want to do anything. When you're extremely lazy, chances are you still do other things.

When you're lazy, you are choosing not to do stuff because you don't feel like it. When you're depressed, sometimes you want to do things but you just don't have the energy to do much but sit and do nothing all day.