Can you feel lonely in a crowded room?

Been a while since I last visited this place of darkness. This one hole in my soul that apparently my mind likes going back to. I don't know how else do I describe feeling this way. From a girl who is considered good at understanding other people, the way they feel, why they feel that way, and how to help them feel better, it seems pretty ridiculous, I know that.
Have you ever felt like you were drowning in this big ocean of doubts and insecurities? Like nothing that you ever do or think is good enough? They say that when your heart is at the right place, things will work out. They say that you should never give up hope because hope is like that burning candle that we ignite when the power gets cut off. But that's what they say. They don't know that in that split second of lighting up a candle, the mind wanders, and the heart tremors. So, how dare they say that it will be fine?
I know that negativity does not suit me. I am a positive person. My whole life is built on hope. But this hole of darkness that my mind keeps taking me back to has swallowed that aspect of me. I am lost and I don't like being lost.
So, is it possible to feel lonely in a crowded room? Apparently it is.