I'm sorry I have nightmares and wake up sad. Because the nightmares are real.

You should stop apologizing. I understand it's hard for people to grasp something like PTSD, especially if they don't have it. But if they're not going to make an effort to try to be empathetic and understanding, they're not worth your time. Though you may not know me, I'm here if you need an ear. I deal with the same things with the nightmares/memories, episodes, the whole nine yards.