I believe there is heaven and there is hell – period. None of us is good enough to get to heaven. If someone is telling you that, then you need to seek more spiritually mature counsel. The only way to get to heaven is to confess that you are a sinner (like we all are), acknowledge that Jesus died in payment for your sin and that He rose from the grave. Grace is a gift. We feel unworthy–and we are unworthy–but you just have to accept it. It’s the most humbling feeling you’ll ever have (and the best). As far as the scriptures you reference from I Cor., you have to read the verses before & after to get the context. This is an illustration of resurrection. As there are differences in the celestial bodies and the terrestrial bodies, so is there a difference between the physical body that is sown onto the earth (our physical bodies which are perishable and will decay) and the glorified bodies that God has in store for us (which are imperishable and will not decay).