Questioning my own existence

It doesn't need to be answered. It's only the anxious mind that feels the need for all these questions to be answered. You need to regrow your tolerance for uncertainty. Because no one has the answers to existence. But that doesn't bother normal people. Why? Because a non anxious mind has a playful tolerance for the unknown. Put your Iphone down, reconnect with nature and beauty. Go for a beer with some friends, text a girl (or boy) you like. My mind stopped questioning when I started living like a free man again

Exactly, these questions are inherently meaningless and you can never be certain about them. They don't matter, at all.

Like Al_pk says, reconnect with life, lower your anxiety levels, and the questions will go by themselves. Don't obsess about finding answers, you won't and it only makes everything worse.

As a general rule, Descartes stuff is not to be dabbled with whilst your brain is unhealthy and in DP. It will just lead to panic and obsession whilst you can't let go of it because thoughts stick to the mind like glue. No, you need to go towards grounding and reality.