If it's under 25,000 posts, the "Forum Posts" achievement tracker does the trick!

Just use the achievement search and check for the word post, it'll pull it up!

I believe it's every 750 forum posts that gets you a star.

Good luck! Posting on the forums is sometimes awarding those awesome forum boxes at the moment, too, so that's cool. Just remember not to get spammy and you'll do great!

Ugh thank you. I'm suffering from serious sleep deprivation via newborn, obviously. xD