說不出口 英文係咩?

I am speechless. OR I lost my word. OR It's hard for me to say (tell you)

e.g. I miss him so much, but I am too embarrass to tell him.

Reason: here because you are nervous, embarrassed so you can use this

e.g.2. It's hard for me to tell him: Could you be my boy friend!

Reason: You are in difficulty in telling him directly your wish. You are afraid of his rejection. Thats why It's hard...

But in all the above circumstances you are not using 講唔出口 in front of 他, actually you are talking with the 3rd person about your difficulty.

Hope you can understand my explanation

Words I wanted to say just couldn't come out in front of him.

Hi there,
但對住佢又講唔出口
1) I do miss him loads, but every time I face him, I have a brain fart.
2) I've missed him so much, but when he is in front of me, the words just won't come out.
_______________________________
3) I have no feelings for that guy, but I don't want to hurt his feelings by telling him the truth.

That's how I would say it.
Hope that helps.
Until next time, bye for now.

"i really miss him, but when i see him i would be speechless"

I dare not say in front of him

說不出口----------Said that does not export......

You can say.... my brain is empty when I am in front of him

OR

"It is difficult to say a word" when ..... something something...