You don't want lumbar mobility anyways unless you want an unstable spine and pelvis... Not good.
Increase your hip and thoracic mobility. Work on stabilising your lumbar spine/pelvis and scapulo-thoracic joint. Go search for hip mobility exercises and thoracic mobility exercises (foam roller or two tapped tennis balls). Stretch what is tight statically, add a good dynamic stretching warmup (of which your hip and thoracic exercises should be a part of).You could do most of this in a warmup/warm down for work out.
Get yourself a good massage or foam roller and massage ball the crap out of yourself a few times a week especially in your glute medius and piriformis along with your whole shoulder girdle area.
Add something like glute bridges, lateral band walks, wall slides, prone y's and t's, pushups, two leg lowering (move to swiss ball rollouts, then barbell rollouts then an ab roller and focus on a neutral back and non moving pelvis) to your workout. You want to activate and strengthen the weaker inhibited muscles such as your gluteus medius and glute max on the non-tight sides, your lower trap, serratus anterior and rhomboids.
Some good educational stuff for you would be 'A Joint by Joint approach' by Mike Boyle (search for the title on google), Magnificent Mobility DVD by Robertson and Cressey, Gray Cook and Lee Burtons work.
You do not have to go all functional training style but bringing in some would help you in the long run, just don't sit on a fucking swiss ball and do your exercises like I see some PT's make their clients do
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