How do you know your spirit never existed before you came along?And how are Buddhist Atheist?

Okay I truly believe that we existed before our body existed and that gives good reason to why it is important to take care of mind, body, and soul. Has anyone ever had that feeling where they wake up overjoyed and they feel as though you're more than just this body, you're something else? Because I have and let me tell you it feels amazing. Another thing, I read a few comments from Atheist and they said Buddhist are Atheist and that's something I don't understand because my boyfriend is a Buddhist and he may not believe in God but he has spirituality and most of you Atheist don't believe in having a spirit and you believe that when you die, that's the end. That's a contradiction though because Buddhist believe in reincarnation, and living many lives before they finally reach nirvana, become one and reach enlightenment, which is more of a spiritual feeling so I don't look at Buddhist as Atheist because clearly they believe in life after death, or their souls wouldn't journey to another body to live a new life. Any answers and oh can you all those, who do know what I'm saying answer my question?