Hi sui, I am sorry you have these flashbacks. Remember they come on like a wave and then they always recede. Feeling worthless or unworthy is also very common with people who struggle with PTSD. It is important that you find a good therapist to help you work through this, listens well, and you feel safe with. PTSD also presents fearful feelings, the emotional challenges that take place with PTSD are challenges all people struggle with yet the PTSD magnifies. It is also not unusual to have sensitivity to crowded places that are also noisy, so if you are at a loud party with a lot of activity taking place it can get you aroused/hyper sensitive and uncomfortable. People with PTSD are stuck in hyper arousal so they like to keep their environment quiet and safe if they can. Yes, night can be more of a challenge too because it is hard to just shut down when hyper aroused at the same time.

Are you taking medications and seeing a therapist?

(((Sui)))
Panic attacks are the worst, huh?

One of the things that I've found helps me most is, believe it or not, breathing. Because when you are panicking attacking, you tend to be usually hyperventilating (am I right?).
So this is actually a DBT skill that I learned in the hospital, but it's really helpful, called 4x4 breathing...
Breathe in deep for 4 seconds, hold it for 4 seconds, breathe out all the way for 4 seconds. Then repeat that 4 times.
That, and also find a "reality object". For me it's my stuffed cow. I hold her/violently squeeze her when I need something that's outside of my mind, something that is real, in this world, something that will help anchor me back to reality.
Once you've done that, splash water on your face. Or dunk your face in a bowl of ice water, if you need the extra kick.

I hope that some of these tips help! And you certainly don't have to feel like you're the only one, mijo!