I suggest you re-read Doctrine and Covenants section #132:
http://scriptures.lds.org/dc/132
1 VERILY, thus saith the Lord unto you my servant Joseph, that inasmuch as you have inquired of my hand to know and understand wherein I, the Lord, justified my servants Abraham, Isaac, and Jacob, as also Moses, David and Solomon, my servants, as touching the principle and doctrine of their having many awives and bconcubines
2 Behold, and lo, I am the Lord thy God, and will answer thee as touching this matter.
3 Therefore, aprepare thy heart to receive and bobey the instructions which I am about to give unto you; for all those who have this law revealed unto them must obey the same.
4 For behold, I reveal unto you a new and an everlasting acovenant; and if ye abide not that covenant, then are ye bdamned; for no one can creject this covenant and be permitted to enter into my glory.
.....
I have read it many times. You do not understand it.
The covenant of marriage, in this case plural marriage, is "new and everlasting", not the practice of plural marriage. In other words, those plural marriages performed under that command were to be an eternal covenant. The section does not say that practice of plural marriage would be "everlasting".
Do you understand the distinction?