No estoy seguro + algo en el futuro - cuando no hay un cambio de sujeto
Por favor, ¿cómo se dice? - I'm not sure if I will be nervous.
No estoy seguro de estar nervioso. (my favourite)
Ne estoy seguro de esté nerviouso. (I don't think so)
No estoy seguro de que estaré nervioso. (hmmm I want it to work but am not so sure)
(oh and another)
No estoy seguro si estaré nervioso. (as above lol)
O ninguno de las anteriores je je 
¡Gracias de antemano por su ayuda!
My dilema comes from using 'no estoy seguro/a' which is followed by 'de que' and the subjunctive if there's a change of subject. But I just can't remember what to do if there's no change of subject - although my brain says use the infinitive I also somehow want to indicate the future.
11 Answers
Hi Kiwi!
I'm not sure if I will be nervous:
No estoy seguro si estaré nervioso is a very common way to translate your sentence. And it's my favorite.
But, "no estoy seguro de estar nervioso", "no estoy seguro de que estaré nervioso" and "no estoy seguro si estaré nervioso" are different ways to say "the same thing" (la misma cosa).
Like:
"No estoy seguro si estaré aqui cuando tu vuelvas".
"No estoy seguro de estar presente cuando ellos se reunan".
"No estoy seguro de que estaré listo a esa hora".
"No estoy seguro si volveré mañana".
I hope to be helpful. This is the best way I can explain it >_< y no estoy segura si lo entenderás 
All right just to keep this clear:
In conclusion ....
no estoy seguro si : is followed by the indicative, regardless if there's a change of subject or not
no estoy seguro de que : is followed by the subjunctive if there's a change of subject but by the infinitive if there's no change of subject
No estoy seguro de que me entiendas. I'm not sure if you understand me.
No estoy seguro si me entiendes. I'm not sure if you understand me.
No estoy seguro de entender. I'm not sure that I understand.
Hi, Kiwi, Wordreference.com has an entire thread on this; I found it by typing in a search on their forum.
The native speakers there would indicate: "No estoy segura si voy a estar nerviosa".
Can any native speaker confirm the conclusions?
The fourth one, no estoy seguro si estaré nervioso, works for me.
Edit:
Also "No estoy seguro de que vaya a estar nervioso" and ""No estoy seguro de que esté nervioso" seem good to me.
Yay finally it seems that RAE has come to my rescue:
"388h. Cuando la duda se refiere a lo futuro y el agente de los dos verbos es uno mismo, no es indiferente el uso del presente de subjuntivo o del futuro de indicativo; o sea que no es lo mismo decir 'no sé si salga' y 'no sé si saldré'. En el primer caso damos a entender que el hecho de la salida depende de nosotros mismos, y que no estamos resueltos ni decididos a salir o no salir; en el segundo manifestamos que el acto de salir es independiente de nuestra voluntad."
That is - when the doubt refers to the future but the agent of both verbs is the same person you can use either the present subjunctive or indicative future. (referring I presume to saber si or any verb followed by de que)
It seems that saber si is the only exception to the never follow si by the present subjunctive rule - 'no sé si salga' y 'no sé si saldré'. However when it comes to 'no estoy seguro' it seems we would need to use 'de que' instead of 'si' if we wanted to use the present subjunctive.
But please let me know if I have any of this wrong
This isn't quite the same thing but I'll post it here because it talks about 'no estoy seguro' and has some good insights from Lazarus no estoy seguro
Ah this is driving me crazy!
Ok well so far I'm thinking that if there's no change of subject the most gramatically correct thing to do would be to follow the phrase by the infinitive.
I am uncertain whether to accept ? no estoy seguro si aceptar
However, I think that colloquially the future tense does get used to talk about something in the future.
I'd love to find a definitive explanation though :(
Oh and if there's no change of subject I would go with using 'si' / whether; but if there is a change of subject then I think there would need to be a 'de que' instead.
Feel free to challenge this though je je
Seems I've looked at this subject before but it obviously didn't sink in lol
I vote for the first option - "No estoy sequro de estar nervioso." I think the rule is that a verb always takes the infinitive form if it follows a preposition, especially so if the verb follows the preposition "de." Please tell me if I'm wrong.
But wouldn't that first one mean, "I'm not sure if I am nervous" and is not conveying the sense of "will be"? I vote for estaré, but then, what do I know?
