Husband cheated

Just found out my husband cheated on me. I suspected something. I asked the girl. She called me and told me they had sex once. He said she was lying (obvi don’t believe him). Honestly I think I’m numb. I’m a big crier and I can’t even shed one tear. Kinda in shock. We live over seas with a four month old. Both in the military so I can’t go back to the states. I don’t even know what to do... I’m lost...