To quote Matthew Henry commentary:
Man is a strange sort of creature, a ray of heaven united to a clod of earth; at death these are seperated...The soul, that beam of light, returns to that God who, when he made man of the dust of the ground, breathed into him the breath of life, to make him a living soul (Gen 2:7) and forms the spirit of every man within him...It goes to God as a Judge, to give account of itself, and to be lodged either with the spirits in prison (1Peter 3:19) or with the spirits in paradise (Luke 23:43) according to what was done in the body.
The scripture that Swing has referenced does not state that we pre-existed, it is just the way that the Mormons twist scripture to conform to their heretical doctrines. In order to understand where Swing is coming from...you need to understand the "complete" Mormon doctrine regarding this. They believe that their god (who is just one of many gods) is in heaven with his eternal bride and many concubines having sex and making babies. These babies are their "spirit children" who must come to earth in the form of a mortal in order to complete their exaltation to godhood themselves. It is all part of their doctrine that "as man is...god once was, and as god is...man may become". By the way...Mormons also believe that their god's higher, more evolved or somehow advanced spirit children are born to Mormon families here on earth.
We were created, at the moment of conception, and became eternal beings at that time when God breathed His spirit into us. While our mortal bodies will decay and return to the earth, our spirit will return to God, not to resume some heavenly pre-earth existence, but to be judged. Where we spend our eternity will be completely by choice, in heaven with God or eternally damned to a place created originally for Satan...hell. Because God states that He for-knew us does not mean that we pre-existed, only that God is all-knowing. We exist within the framework of time, but God being outside of time, knows each and everyone of His children and also knows who will choose eternal life with Him through His Son, Jesus Christ, and who will reject Him. I pray that you are one to choose Jesus!