What you've been through must be very traumatic and painful for you.I have endo on the bowel, (not in the bowel) and certainly not to your extent, so I'm not sure that my advise would be of any benefit. however, I can tell you what it's like for me, and maybe it might make you feel better just to know someone else going through something similar. My endo pains started in 2005 - we all know they feel like the worst period pains in the world, when they attacked (1st day of period) I couldn't walk, I could only lay down for about 5 hours, and then magically it would disappear. Then the dreaded cycle would appear again and again..
Two years later, every time I went to the toilet (not wee!) I would get a short burst of similar pain - made going to the loo so difficult, but gradually, I started improving my diet, lots of fibre, more water etc. and it did really help. Didn't stop the rest of the pain but after my laparotomy I felt so much better. Since then I've been on progesterone which meant I still have periods, but I was more in control of the cycle, making the cycle more predictable was much less stressful, the periods were much less lighter. I also controlled how much progesterone I was taking depending what the day of the months was, i.e. between 5-12 less, 13-25 more progesterone.
I had to come off the medication a while ago because I'm going through IVF. My first cycle, in fact, today, has just failed due to an almighty period, and I've been beginning to notice more pain going to the loo again as well. So I guess I'm still living with it!
I guess what I'm trying to say overall, is that for a time my condition was managed well, but admittedly this was through private care. In order to achieve pregnancy (maybe), I have to literally just put up with it, but you just, survive somehow!
Your endo in the bowl sounds more severe than mine as I dont bleed from the rectum, so I can only offer understanding - but at least I can say that my condition was managed very well. Don't be afraid to seek advice, or a second opinion. My consultant was also an endometriosis specialist (amazing how some obs and gynaes doctors aren't!), so it's worth seeking this specialist opinion out. If a treatment/management plan is set in place you can always go back to a local consultant to manage your plan. I hope that all makes sense?