I can’t speak to your pms issues b/c I was menopausal by the time I got my dx, and I will buffer this by saying I tend to be highly sensitive to most med/lifestyle changes (good & bad), but I did get a discernible boost from my very 1st dose of Dexedrine. It was as if somebody blew dust & cobwebs out of my head allowing me to, literally, SEE more clearly, and I accomplished more that day; it felt like a magic bullet… for the first while, at least. Over time, its affect was less profound & increasing the dose past a certain level was unsustainable due to side-effects like your jitters plus a lack of appetite, insomnia, etc, that mimicked hypomania. Now, at a steady, low dosage, I don’t really feel it except when I miss taking it (if I’m having a challenging or scattered day I’ll often find my daily dose is still waiting for me).
To address your other Qs:
You are NOT out of luck. There are many different ADHD meds with different active ingredients. Keep trying.
Yes! Diet & hormones, and many things, profoundly affect the biochemicals that control our mental health. Keep reading! (to get started, maybe google “William Walsh nutrient therapy” or “ADHD diet” or “pms supplements”)
Ask the pharmacist if there’s any negative consequences associated with stopping the Ritalin & see your doc asap to get something better for you.
As life-changing as it can be, medication is definitely not a be-all-end-all (or magic); it’s just one tool among many. I wish you luck with all of it!