Slander/Oral Defamation

I just want to seek legal advice lang. Yung ex kasi ng bf ko now is spreading gossips about me and my bf. Pinagkakalat nya na i already have a child bago pa naging kami ng bf ko and that i am pregnant now. These are all lies. Iignore ko sana kaso bawal sa company na pinagtratrabahuan namin ng bf ko (different departments kami) yung having a child beyond the course of marriage. May kaakibat na sanctions dun which may lead to 30 days suspension. Aside from that, people are prejudicing us since the rumor started. Can i file a lawsuit dun sa ex ng bf ko? hindi ko nga sya kilala personally e. Di ko alam bakit sya ganun sakin. The problem is, ayaw magtestigo ng witness na nakuha namin. Ayaw daw nya ng gulo. Pero merong admission from the mother nung ex ng bf ko na sa ex nga ng bf ko nalaman yung rumor. Please help.