This sounds like Sciatica. The sciatic nerve is the main nerve running from the spine down each leg. It runs right past the very places endo usually nests on the way and is often getting caught up either directly with endo growing on it or more commonly with adhesions which stick to it.
It can affect both legs but usually one side is the problem.
Surgery to cut away endo and cut back adhesions can provide a lot of pain relief from
sciatic endometriosis .
There isn't really any pain killer that you take orally that will do a great job. you can have nerve blocking injections to kill the nerve pain signals, but they are temporary and not nice. It is far better to have the problem removed if that turns out to be endo or adhesions.
Another thing is ovarian cysts, they can get weighty and be resting on the sciatic nerve when you are sitting or lying at certain angles and cause irritation to the nerve too.
not many regular gynae surgeons are familiar with sciatic endometriosis . It is fairly newly identified - 1955 onwards.
but there are enough cases on this forum to know that although still a rare one, it is one that surgeons should be looking for when they map your endo.
this website is a fancy one - best viewed on firefox or a very up to date browser
it has a lot of good info on the surgery that is needed....and surgery is certainly an option despite what your consultant has told you.
here's a you tube video on it - warning it is graphic if you are squeemish about seeing surgeries.
and another website
which includes spinal endo too.
There are plenty more websites mentioning this - i would print some URLs off - selected paragraphs too - and armed with that see your GP or specialist about getting a referral to a specialist surgeon who does this type of surgery, or contact medicare if you are with them and find out what specialist surgeons are operating near to you on this type of condition. You could well have to travel some distance, I wouldn't imagine there are too many such surgeons around.
don't give up just because one doc says there is nothing more they can do. if this is endo - there is a lot more they can do, you just have to do the donkey work and find the right person to do the job. Best of Luck