From what I know of Membranous Glomerulonephritis (MG), exhaustion or pain are not from the 'disease' but perhaps from the meds or could possibly be a different health issue altogether. Do you have a primary doc you have spoken with on these issues? Or perhaps start a different medicine regimen.
First off I am 41 and female. I found out I had this just under 2 years ago after admitting myself to the ER with severe chest pain. Turns out I had multiple pulmonary embolisms on both sides of my lungs. I've never been sick or ill and had just delivered twins a year and a half earlier with no issues during pregnancy. Although I did have 3 similar separate episodes of chest pain the year and a half before diagnosis, symptoms would always go away within 24 hours. I figured it was a consequence due to the preghancy or aging or something. Needless to say this was a surprise, the clots. They realized I was leaking protein right away and after various tests and then kidney biopsy, MG was my diagnosis. I took and still take warfarin do deal with the clotting. I was taking a statin but didnt feel good on it at all so took myself off. Fatigue, muscle ache or cramps, I was also forgetful. Hated it. Doc then gave me niacin to take, took sporadically. Just tried to better my diet.
SO my case is different for not only is this a rare issue, but I am a rare patient. youngish healthy femaile, no high blood pressure, no thrombosis. So I am not taking any other meds than those above. I can't.
I had a protein number of 6-8000. It's now down to 370. I had cholestrol number of over 500 it's now down to 223. It takes time but so glad to see a decreasing trend on these numbers.
Again, I'd suggest having docs look at these symptoms you have, run blood tests, and figure out what else it may be, besides the kidney issue. Or change the meds. As for how serious MG is, give it 18 months and see if it worsens or improves to know if it's a threat or not. I think for a third of folks, it can get worse, for another third, stays the same, the last third, goes away. If it gets worse, it can impact your kidney function.
Also, please watch your diet. Eat better! Less cholestrol, less red meat, dairy, less salt, more greens, more water.
Keep in touch with updates. Hope it starts to turn the tide soon for you.
It's so hard to see him struggle and we just wish could get more definitive answers as to why and are we really doing the best to 'reset' his system so this unkonwn autoimmune, which is what they say, will go away.