there are 3 types of karma, if you don't know which one you belong to then you amount to about the same as someone who doesn't know the bible scriptures.
It is important that we NOT entertain our own understandings of afterlife, immortality, spiritualism, christianity, etc. We know nothing about these things on our own and always we have grabbed a concept by reading about it or hearing it from someone else.
If you follow karma then you will be back to a world that eventually doesn't exist, according to the bible.
Isaiah 65:17 For, behold, I create new heavens and a new earth: and the former shall not be remembered, nor come into mind. (This is an old testament prediction)
Revelation 21:1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea. (new testament revellation)
The bible again reviles reincarnation:
Hebrews 9:27 And as it is appointed unto men once to die, but after this the judgment:
You use the word rebirth, the bible says "born again". The born again of the bible is instantaneous and here on earth via the salvation process.
John 3:3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
John 3:7 Marvel not that I said unto thee, Ye must be born again.
1 Peter 1:23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
a further explanation of salvation:
Romans 10:10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
You also mention heaven and hell. Very difficult to explain in a short reply. Heaven is undisputedly where god lives or the center point of gods existence, since god is a spirit and is in all places and everywhere. God is not in the universe persay but the universe is in God. Hell, you will find many concepts of hell right here on hub pages, most are wrong but you get the idea. You asked for the truth. Truth is relative, as a christian i purport the bible is truth. As a karmic follower you may prefer the gita book.
The truth, only you can find out and i wish you luck or revelation by god on that. Luck comes by imagination or carnal thought, revelation by god, comes through asking god whats real and being open to what his spirit says.