The Ready State Virtual Mobility Coach is like having a virtual Kelly Starrett in your pocket.
The first thing is to identify the cause of “I always loose my lower back to over extension”
Have you addressed the “anterior pelvic tilt”?
This is the place to start.
It can take time to get your breathing in order. Repetition so it becomes the way you breathe with the skill.
There is a good series with Jill Miller on fixing your breathing
Jill Miller Fixes Your T-Spine and Crappy Breathing Mechanics
Jill Miller Smashes Your Guts! (and psoas, and tacked down viscera, and matted down abdominals…) Part 2
Jill Miller Diaphragm Evolution Part 3: Eccentric Loading
There may be something here that is restricting your ability to breathe the way you are looking to.
Focus on one aspect at a time.
Identify which correction will have the biggest impact and hit that first.
That way you have one thing to focus on correcting and you will see a lasting change.