一ヶ月たと!?何と長いよ!ごめんなさい!
Holy crap, it's been a month [since my last post]?! That's so long! I'm sorry!
一ヶ月たと→ doesn't work as a stand-alone expression. Or, it works, but not for the sense that you intend it to mean. By itself it is more of an expression of surprise you would target (aggressively) at someone else ("
What do you mean 'one month'?"). And, I think you meant だと instead of たと?
何と長いよ→ Again, doesn't really work as a stand alone expression, and doesn't combine well with the previous one to form a complete thought. From the previous phrase we can get the gist that you are talking about the "one month", but it doesn't work here.
Omitting the key bit about "since my last post" is confusing for the reader, and makes the reader guess at the meaning of the "one month".
ごめんなさい → OK, this bit is fine, but the apologetic tone clashes with the first two bits, which sound more accusatory or plaintive.
So...how to fix these to form one coherent statement? Something like
一か月ぶりのブログポストで、たいへんお待たせしました。But that is a bit formal. Or, この前の投稿からもう一か月たってしまったっけ?ごめんなさいね。That's a bit more colloquial and familiar. But it is difficult to be colloquial and friendly in Japanese if you don't have a good grasp of the concept of politeness levels. I've been learning for 30 years and even I don't have great confidence that my two examples above don't have some kind of error in them. Anyway, familiarity is something to be handled with caution, as its easy to be unintentionally rude..
You can see why your study habits are letting you down in a big way, and you can get a feeling for how difficult it would be to fix large chunks of your text.