Are you supplementing with progesterone cream? That would be beneficial to short LPs. And for my own information, Paraguard doesn't have artificial hormones... so I didn't think that would mess with a woman's natural hormone cycle?
i'd also wonder about the possibility of O on CD22 with a 2DPO fallback rise ... making it a 10day LP (if you started your period.) It doesn't match up with your OPKs, but it might be a possibility.
Either way - best of luck to you. :) Hope things even out for you and your cycle after your IUD.