Ramir,
Don`t beat yourself up about it. A lot of musicians have trouble with that sort of thing. That`s why musicians who have good ears have transcribed such things as solos by John Coltrane, Charlie Parker, Miles Davis, Dizzy Gillespie, and the like for the musicians who don`t.
Just because you don`t have perfect pitch doesn`t mean that you aren`t a good musician. If you focus on your technical and sight-reading skills, and master them, then it won`t really matter.
Remember, Ramir, not everyone is born a Mozart, a Beethoven, or a Bach.