I'm really depressed about being 30.

I've been 30 for several months now, but my 30s are off to a really shitty start. I am feeling more miserable than I've felt in a long time, and like time is passing me by too fast. I'm terrified of losing loved ones, having my best years pass me by, etc. I honestly had a horrific adolescence and 20s, and I feel robbed there already, and I feel like my window for so many things is closing. I have zero desire to get married (or even get into a relationship) or have children, so I just don't see a reason to even look forward to the future. I've pretty much already done everything I wanted to do, that was within reason or attainable. I've met all the milestones I'm going to meet. I am deeply unhappy, too.

I keep being told, "You have no idea how fast 30 to 50 flies by!," and that a lot of loss starts in your 30s. That terrifies me, I want nothing to do with it. It just makes me feel like the future is very bleak.

No, I'm not in danger. But I am absolutely miserable, emotionally exhausted, and dreading the future. I really don't know what to do, or even what I want. I don't even know why I'm here. I guess to get it off my chest.