So, let me ask you directly: Do you believe that to contracept is to sin?
Secondly, do you belong to a church which teaches it is a sin to use artificial birth control?
Do you, or do you not, believe all forms of contraception to be sinful.
If you do not, on what scriptures do you base your belief?
If your church does not teach contraception to be sinful, by whose authority did it change the continual teaching of Christianity on the subject?
If it did not have such authority (which it obviously does not and cannot) then your system is in apostacy, and you have no grounds whatsover to challenge the scriptural interpretations and doctrines of Catholicism. Period.