Lengthening Luteal Phase?

Anyone have and luck naturally lengthening their Luteal phase? I start spotting and then AF arrives only about 5 days after ovulation. It's been this way since my D&C in July. My OB seems to think this is probably why I've lost 2 pregnancies since then but wants to either refer me to a reproductive endocrinologist or just do progesterone after I get a bfp. Anything I can do in the mean time? I don't really have the $$ for a reproductive endo right now. TIA!