You will can use Minecart to go up after Bedrock. Steps:

1. Go at X=~ Y=123-126 Z=~
2. Break one block forward (if it's not Bedrock)
3. Place Rails
4. On Rails place Minecart
5. Get in Minecart
6. Throw enderpearls in Bedrock
7. Try to fly out up
8. Done.