Pre-term labor?

Hello good evening mommies, i am 29 weeks pregnant, and 3hrs na po parang nagcocontract yung tiyan ko hanggang singit. Naninigas siya. Minimal pain. Pero 3-5mins ang interval ng paninigas. Anyone here na may same experience? What to do po? I tried to call my OB but she's unavailable. Pls help me.