You can use either sentence, but they may not mean the same thing. It is not clear that they both refer to the same emotional situation. The first sentence sounds like you are yearning for her; the second one sounds like you are annoyed with her.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Doctor DBy the way, although there is nothing wrong with the sentences, a more effective sentence would be to place the "frown" clause at the end:When I realized/Upon realizing the impossibility of having kids without her, I suddenly frowned.But if I write When I realized/Upon realizing the impossibility of..., does this sentence still mean that I'm an