Sorry to hear about your endo and the decision you have to make.
I too had severe endo and had to have a laparotomy last year which took 5 hrs as I had a bowel surgeon, a urologist and my gyno all work on me to get rid of it all. My FS told me that IVF wouldnt work unless I had the op. Afterwards, I wasnt given the option of IUI but my DP sperm is a little iffy too so we went straight into IVF.
Endo can spread. With every AF it gets worse. I had a lap about 8 yrs ago in which they removed the endo and then put me on medication to stop AF for 6 mths to help it. However it eventually came back and hence my operation last year.
Good luck with your decision. As other girls have suggested, Id be asking more questions about IUI as you dont want to waste more time than you already have. If doing IVF will get you your BFP sooner, then Id be heading done that track
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