I had the severest grade most agonising endo, probably from my first periods when I was ten, though it wasn't diagnosed until 23. I had Zoladex for that, which helped quite a bit. I only ttc at about 35, and had recurrent miscarriages, but finally had my son at 38. I now don't really suffer from the symptoms of endo, though I haven't had a scan so don't know what's really going on in there! I now have a short luteal phase though; how many more gynae problems can one woman have? I just need PCOS and premature ovarian failure for a full house!
But to answer your question, yes, perfectly possible, even with the worst endo. Good luck!
xxx