Congratulations. Its not uncommon for people to Astral Project on reflex when they first read about it. Before you get into the Semantics, semiotics and proxemics of AP (oh yes, they are big words
) try again, you might find you don't have the ability to do it until you acquire more skill.
As for your question...you can create thought forms in the first couple of levels but its hard to keep them solid and as you rise through the levels they become decidedly more....solid, in a non-solid way.