Short luteal phase?

I have a 10 month old and been trying to conceive a second since my husband and I aren’t getting any younger. However, my period keeps starting 9-10 days post ovulation and I’ve been spotting from 3dpo onwards. Has anyone else dealt with this? I have a doctor appointment in a couple of weeks but wondering what others have experienced. The internet says possibly thyroid issues or low progesterone could account for the short luteal phase but I’d love to hear from somebody who’s been in this situation before. Thanks!