In this talk, I will show how the attractive self-interactions of fuzzy dark matter (DM) can lead to nongravitational growth of density fluctuations and the formation of bound objects. This structure formation enhancement is driven by parametric resonance when the initial field misalignment is large, and it affects energy density perturbations on length scales of order the Hubble horizon when the scalar field starts oscillating, deep inside the radiation-dominated era. I will also explore some observational consequences of this mechanism, for example, the stellar secondary stream and pulsar timing array