How to extend luteal phase

Hi, so we have a 2 year old girl who we fell with very quickly and with not much tracking etc but this time round it seems to be taking longer.

I have been tracking my ovulation using digital tests and have worked out that I only have a 9/10 day luteal phase. After doing my research chances of pregnancy are not good unless I do something about it really and it's getting me down as every month I think it could be implantation and it's not.

What can I do or take that can help to lengthen this phase and give a fertilised egg time to implant?