Thinking is Sensing

Descartes' philosophy that we cannot trust our senses made me think. If we cant trust our senses, how can we trust that what feels or looks real is real? If he says "I think, therefore I am." Arent our thoughts developed by what we sense is important or real? Since we can't trust our senses, how can we trust the thoughts that derive from them? I feel that Descartes' metaphysics lead to the conclusion that we cannot be sure of anything that he is sure of. One cannot be certain that they exist without it leading back to the senses of sight, hearing, taste, smell or touch. To know what something mean, one must have prior experience that teaches them the difference. That experience has to utilize the senses. Based on Descartes' classification of the senses as unreliable, one cannot truly know anything.