Is there a way to delete all of my forum posts all at the same time?

It doesn't. You may only delete all once by once
Only moderators can check more than one post on a thread

You can ask a smod to delete your posts if it really is a huge amount of it's like 10 just do it yourself

No, and you also can't delete any posts in locked threads.

I advise you not to worry too much about the things that have been said and done by yourself in the past. We've all been there. If you want to have specific posts deleted (e.g. you're afraid your e-mail or something else sensitive is somewhere on the forum) then try Googling this info and delete those posts. If the info is in a locked thread, just report your post and ask a moderator to delete it for you.