From IUI to IVF with miscarriages ... Help please!

I have PCOS and Luteal phase defect... I do not ovulate and it is difficult for me to get pregnant... However, I have had 4 pregnancies.. 2 natural, twins from IUI, then another natural... All of which I have miscarried.  They have no idea why I am miscarrying; I have had a full blood panel done and everything seems normal. Is there a point to moving on to IVF at somepoint? Are the chances of me not miscarrying any better than with IUI or naturally?   TIA