What is there to tie you to what you said? How can they prove you said these things? It could have easily been someone on your computer. You could have just been playing around and having a laugh at all of the nuts here!
Internet forum posts are likely super low on prosecutors lists of how to get people. I doubt a judge would grant a warrant for such a thing. Plus, this site specifically would be low in priority, with its strict no distributing talk.
Are there people form the government cruising sites like this? You bet! But when the day comes that they are hunting down individual users of psychedelics from their forum posts, we'll have bigger issues.
There's really not much to worry about. Go about your life, and if you get spooked just quit posting.
Be an adult only when necessary.