I have two different words for I couldn`t come

gelemedim and gelemezdim

which one is correct please

Does the second one even exist?

Exists the second one too... im also waiting to find out the difference.

In my opinion,

Gelemedim. unfortunately I couldn´t come, it is related to me or something happened on the way. I wanted or tried but it was not possible. I will come next time.

Gelemezdim. I couldn´t come, because there was a reasonable excuse. Actually I could come, but I didin´t prefer or choose coming. I didn´t set off. Also in this situation I probably can´t do next time too. You should not expect me to come in this situation.

I know I couldn´t explain, but tried. Their meaning is very close. You can use gelemedim instead of gelemezdim, it doesn´t matter.

Acıklaman için teşekkür ederim

Merhaba,

What´s about gelmeseydim? Doesn´t it also mean I could not come?

Doesn´t that mean ´If I didn´t come´ ?

 if....

it does

I totally agree with the explanation but I do no agree really that they can be used instead of each other. "gelemezdim" really makes the sentence dramatic in a way that you had no chance of coming.