I'm having a strange pain in my left ovary and not sure why. Already ovulated, period comes in a week, and I'm TTC. Any ideas on what it could be?

Judge by pain nature. Due to the fact that intra-abdominal pain is not precisely localized, it's hard to advise in your case. Your symptoms could be caused by ovarian cyst (i.e., corpus luteum cyst), chronic adnexal condition if any, urinary stones, intestinal problem to name a few. If the pain is mild and self-limited, most likely it's not serious. If it's prominent and persistent, then Gyn evaluation is required.
Could be a cyst. could be a cyst in your left ovary gut tense or ruptured ,any of these possibility could cause adnexa pain. see your GYN for ultrasound that could determined the status of your left ovary.