One of the hardest things to do while depressed (and even afterwards) is talk about it with other people. This is unfortunate because in order to get treated properly you will need to let others know sooner or later. There are many reasons talking can be difficult:
You are embarrassed
A lot of people think of depression as something that happens to someone else, someone not as strong as them. Actually, around 10% of adults in the US suffer from a mood disorder in a year and around 7% of the population suffers from depression in a year (Source: NIMH). It's very likely that someone you know is suffering from depression, whether you know it or not. It can be a real blow to think that you might be suffering from it as well.
You don't know what to say
I remember when trying to describe my feelings when I was depressed, the best thing I could muster up was "I feel really sad." That was supremely inadequate to describe the sense of despair that filled me whenever I tried to fall asleep, or the feeling like you would never be happy and don't deserve to. But how do you say that to someone out loud? It's tough, but not impossible
Don't know who to tell
Sometimes it can be hard to tell people close to you because you don't know how they'll react. I know that was the biggest reason I didn't want my parents to know. Luckily, when they did find out they were extremely helpful and really just wanted me to be happy. It can be easier talking to a counselor or therapist, because you know they just want to help you.
Working up the courage to talk is one of the biggest barriers to getting treatment. Please don't let that stop you. Your happiness is important. If you feel depressed now, try to see a therapist or psychiatrist. If that sounds scary, feel free to send me an email at email@example.com. I am not a licensed counselor, but if you just need someone to talk to I am always willing to help. One other community that I have used in the past can be found on reddit.com/r/depression. That is a place where you can anonymously post messages and other people who are suffering from depression can try to give you advice. Ultimately, it doesn't matter if you talk to a psychiatrist, your mom, or your cat. As long as you take the first step of talking about it you will be able to find help.