"給公司發了律師信" -- it sounds like you already have an...

attorney.

i've said this before and i'll say it again: discrimination cases are VERY hard to prove and a lawsuit should not be used as a money-making tool.

with that said, you can retain an attorney and work out a settlement with your former employer. there is a specific clause prohibiting an employer from retaliating against an employee for complaining about discrimination. so depending on your circumstances, you MIGHT have a case here.