Creo que me pone los cuernos

Let's start with the word cuerno, just in case you don't know what that is.   And since "una imágen vale más que mil palabras" - a picture is worth a thousand words, here's a cuerno:

Yes, a cuerno is a horn.  Now we can translate our sentence. 

Creo que me pone los cuernos
I think he's putting the horns on me.

Well, that didn't help much, did it?  Let me explain.

In Spanish, when you "put the horns on someone", "Ponerle los cuernos a alguien", that means you're cheating on your significant other.  Let's take a look at some examples of how to use this.

Creo que me pone los cuernos
I think he's cheating on me

¿Por qué me pusiste los cuernos?
Why did you cheat on me?

Su novia le ponía los cuernos
His girlfriend was chearing on him


Before I forget, there's the word "curnudos".  That's the term given to the parties involved in the affair.

Like always, there's more than one way to skin a cat.  You can use the verb engañar as well, "engañarle a alguien".

Creo que mi esposa me engaña
I think my wife is cheating on me

Mi novia me engaño
My girlfriend cheated on me

¿Me estás engañado?
Are you cheating on me?

¡Me engañaste!
You cheated on me!

Lastly, you can talk about being loyal to your significant other with the words fiel and infiel, which mean to be faithful and unfaithful, respectively.   You'll want to use the verb Ser - Ser fiel/infiel

¿Eres fiel a tu pareja?
Are you faithful to your partner?

Fui infiel a mi pareja en mi despedida de soltera
I was unfaithful to my partner at my bachelorette party

Well, I think that about covers it for today.

¡Hasta la próxima!