20 months and shes not talking!!!!

My baby is 20 months already and she doesnt say anything. She will rarely say daddy just randomly but that's it. She understands both Spanish and English very well. If I tell her to do something she will do it. If i tell her to sit down stand up walk anything she understands it but won't say anything. I'm getting worried seeing how everyone's mids are actually putting sentences together...get doctor will put her in therapy if she still doesnt talk by 2. I'm just worried I guess.