I am using b6 and it lengthened my luteal phase from 10 to 12 days. I took 100mg. You can also take Vitex/Chasteberry, which is great for regulating your cycle including lengthening your luteal phase, which it looks like you probably really need to try something to make it longer otherwise your baby may not be able to implant.
Hope things get figured out! And you get preggo real quick!