tense

[Applejoy]

Is there something wrong with this sentence?

situation : Today is Monday, I sent a message to my friend last Saturday but I'm not sure that time if I was really able to send it because somebody was talking to me while typing it..and my friend hasn't replied yet to my message..here's the sentence:

"I sent a message last Saturday but I'm not sure if I was able to send it."
Shall I say : "I sent a message last Saturday but I was not sure if I was able to send it." which one should I use. " I'm not sure" or " I was not sure". because the action is in the past but until now, I'm not sure if I sent it.Can someone help me?Thanks!

[Casiopea]

Try,

I sent you an e-mail last Saturday, but I'm not sure if it went through.

Note,

Present: I am (e.g., today)
Past: I was (e.g., last Saturday).