The third house rules communications in areas we visit each day, or with coworkers, neighbors, and siblings. Pisces is a gentle, sensitive sign, and since your Mercury is there, it makes it hard for you to assert yourself. Plus the Pisces sun means you see others from a place of understanding and spirituality, so you don't want to hurt anyone.
But you have strong intuition and can read other people well, so I'd like to see you develop that more. Meditation can help that and also calm you. It's a little hard at first to block your thoughts, but as you learn to do it better, it clears the clutter from your mind. There is even an app for your phone called Buddhify, it's cheap, and can help you with short, guided meditations to get you started. I use it when I'm short on time.
Pluto is strong in Scorpio, so that should help with your confidence. You are capable and have courage; you just need to learn to speak your truth more easily. Also, Virgo Moon people are practical, and most people depend on their advice, so you have planets in signs that can overcome that Pisces shyness, and most Pisces people are good storytellers and read others like books. The Mercury means your thoughts are ruled by your emotions, so that can be the issue. But I think you are just getting in your own way.,
I am unsure about the PTSD; you may have a difficult aspect to your Virgo Moon. The Pisces planets may oppose it depending on the degrees the planets are in. Take vitamins and eat well in the days which lead up to your menstrual cycle, meditate, and try to exercise. If you have continued issues, see your gynecologist.