24 weeks pregnant (high risk pg). my mother in law is a devil and she completely stressed me out today. my heart was thumping. could i have hurt baby?

Seems unlikely: I'm NOT an expert in OB, but consider this: your baby will have experienced stress hormones during development and thus will be more able to handle stress better later in life - maybe a future prime minister? Surely all women experience periods of stress during 9 months of pregnancy, don't you think? Suppose you were chased by a tiger (10,000 years ago).