And some topics for you:
Desculpa/desculpe,[1] eu tenho que/de[2] perguntar em[3] Inglês. Eu não sei como (a/o)[4] explicar em[3] Português.
or
Desculpa/desculpe,[1] eu tenho que/de[2] fazer esta/essa[5] pergunta em[3] Inglês. Eu não sei como (a/o)[4] explicar em[3] Português.
1. Comma after the imperative clause is mandatory.
2. For the sense of obligation, you must use 'que' or 'de' after the verb 'ter'. 'De' is more cult and, therefore, in certain regions, specially if you are within a less cult social circle, it may seem as a more serious obligation. It's the best option for more formal writing, but it's not that cult.
3. Using the article before 'Inglês', 'Português', etc. would be exotic. The common is to not use. It's better to not use. But if you want to, it's mandatory to combine em + o (no).
4. You could simply supress the oblique pronoun. But, if you want to use, 'a' would refer to 'a pergunta', and 'o' would refer to 'o algo'.
5. In most regions, 'esta' and 'essa' have the same meaning, colloquially, being one the most used by far. In your sentence, if it were formal, 'esta' would refer to the 'pergunta' close to you and 'essa' to the one close to us. Or 'esta' could refer to the 'pergunta' formerly presented in the text and 'essa' to one still to be presented.
I hope you like the pinpoints. =]