Unexplained infertility

Anyone else in this boat? TTC 3 years. We started seeing a specialist in August. All of our tests have been normal, no blocked tubes, etc. Our fertility specialist has told us that sometimes “unexplained infertility” is truly unexplained. It’s pretty discouraging but we’re trying hard not to give up! 2 failed IUIs and in the middle of our 2 week wait after the third although I’m not confident I’m pregnant. One of my biggest surprises and disappointments has been still not getting answers after seeing someone. We really thought we would at least have an explanation for why we haven’t gotten pregnant yet. Has anyone else been told by their doctor they don’t know why you can’t get pregnant?