What else can I try for a short luteal phase malfunction?

My luteal phase - days between ovulation and AF - is 7 - 8 days. Its been like this for a year and a half, if more. I have been ttc for 2years and had one untimely miscarriage.
I take Agnus Castus (400mg) B6 (200mg) a multivitamin, folic acid and evening primrose oil (upto ovulation) each day but to no avail. I did get a 10 and 11 day LP when first taking the B6 but then it dropped put a bet on to 7 the next cycle.
I even tried Progesterone Cream but only got a 9 time LP.

I am seeing the GP for bloodtests next cycle but really, is that all there is out here to try to 'fix' the problem?
Answers:    How long have you been on the Vitex (agnus castus)? I know it can take several months to show effects sometimes.
I've also hear good things about maca for LPD.
Good luck to you!

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