Forget Candida, it's not the source of your problems.
LBP is a problem and taking some circulatory stimulants would be beneficial but might not rectify the problem.
LBP will affect your circulatory system and your kidneys. Milkthistle can be helpful, it does help me but anything Yin can make things much worse. Therefore if I was you I would look at your diet and things that you eat to make sure that you are not eating a Yin based diet because you need Yang foods to try and counteract the Yin.
BTW you almost certainly have a leaky gut like you suspect, otherwise you could not have lupus. That is caused by an infection in your stomach and with a reflex to your transverse colon.
You might be having anti bodies attacking your kidneys. Do you have any tests that might indicate this?
A herb called Tu Si Zi (Dodder seed) might help. Be aware that it can cause some mild constipation. If you already have constipation then you will need something to counter this such as lecithin. Take as much as needed to cause a bowel movement but go slow.
It might be worth visiting a Chinese herbalist but go by recommendation.