When you first injured your back what did you do to address the cause of the injury?
Did you do any skill/drill work to improve your technique?
Yes you saw a chiropractor, but this fixed the symptom of the injury (pain) not the reason the injury occurred.
 You continued to  injured yourself because the cause of the injury was not addressed.
Your body is able to buffer anything for some time until it can’t any more (ie injury occurs).
Have you worked with a coach on your deadlift and squat technique?
Are you addressing your missing midline strength?
The pain is different  probably based on the compensations your body was making to address tight areas, missing rom etc. Your body will search for tension and slack within the system to feed to a tight/less mobile areas.
There isn’t necessarily a singular traumatic event that caused the pain.
As Kelly notes an episode, and during the Movement & Mobility Seminar traumatic injury/catastrophic events accounts for 1-2% of injuries.
You injury is most likely the cumulative effect of improper technique with the squat and deadlift.
Deviations from proper mechanics will catch up with an athlete over time.
Do you usually squat, deadlift, and bench all in the same week?
Have you had any issues with it in the past?
Pain is a lagging indicator.
Although you may not have felt pain that doesn’t mean there wasn’t deviations in your technique when performing one or all of the lifts.
Did you address the psoas?
One reason you aren’t seeing improvement with your adjustments may be that the adjustment isn’t hitting an area involved with the cause or result of the injury.
Until the root cause of the injury/re occurring injury is identified and addressed you will continue to see different symptoms show up.
What is your position like when you are walking and sitting?
These are impacting factors.
If things are not improving with work it is time to re look at things because you are not targeting the correct areas.
I would recommend seeing a doctor who can give you more information on exactly what is going on with the area(s) that are in question.
What is he recommending you do for PT?