Back/SI Joint pain MUCH worse after losing weight??? Chiro?

Maybe the exercise is making it worse. I have tried 6 weeks of physical therapy with exercises to strengthen my core. That did not work. Now I am trying chiropracty.  Any tips or ideas? The pain radiates across my lower back and makes standing and walking hard.

Keep at physical therapy.  It often takes a lot more time of dedicated (stretches and exercises everyday) effort to see gains.  The back pain is likely due to losing weight and muscle and your body having to readjust to its new size.  If you believe in chiropractic, give it a try.  I've heard, anecdotally, that it has helped some relieve back pain due to weight loss.

Keep at it. Just make sure you are also strengthening your back muscles along with your core.  Everything has changed, I'm about 7 years out and still have occasional low back pain.  Ice and heat can be your friends and a good chiro followed with a massage always helped me.  

Good luck

3 years after my VSG, I just had to have back surgery :(((((  I know all about ****ty back pain. I had my L4-L5 fixed but my L5-S1 joint might still cause me some issues. 

Get x-rays, MRI just to be sure. Back pain isnt something to mess with if it lasts over a long period of time.