Does anxiety symptoms need to be happened every week to be diagnosed with anxiety disorders? what if having it every two weeks and it stops(repeated)?

Depends...: Depends on what you mean by anxiety. If you mean panic attacks, or intense fear with physical symptoms lasting at least 5-15 min, then this could happen episodically (i.e. occur every 2 weeks). Generalized anxiety disorder - excessive worry & physical symptoms tends to be present most of the time, however sometimes the worrying could get worse (i.e. every 2 weeks).