Sorry that you are feeling so bad, you're right you really do need to tell someone. All the online tests can never replace seeing a doctor or other healthcare professional and until you see someone, it is unlikely that you'll start to feel better.

It is really hard taking the first step and telling someone how you've been feeling, but you only have to take that step once. You described quite a lot of behaviours that people around you must have noticed, have they ever asked you what is going on? If people are asking about how you're feeling then don't shut them out, you don't have to tell them everything, just let them know that things are difficult, you're worried and you need some support.

If you decide to talk to a doctor about how you are feeling, sometimes it helps to start the conversation in a neutral way, so rather than jumping straight in and saying "I think I'm depressed" you could say "I'm concerned about my mood and lack of motivation". Either way a good doctor will start asking questions so that you can fully describe what you are feeling.

In answer to the various parts of your post:
I felt depressed for a long time without knowing it was depression. I talked about my mood to a form teacher at school, she was kind to me but it didn't really help. Eventually, when I was at University I talked to a counsellor because I was thinking about dropping out but I felt that would be letting people down. The counsellor told me to go to my doc helped me work out what I needed to tell the doc. Once I saw the doc, he put me on antidepressants but even then I wasn't sure that I was depressed. So even though I knew something was very wrong, I didn't think I was ill enough to be depressed.

My mom and siblings have all been supportive of me since finding out about my depression and that was 3o years ago now.

So please try and talk to someone soon and that way you'll know for sure what you're dealing with.