Overwhelmed and Frustrated: Dealing with Anxiety

i just sh for the first time in over a month because im about to buy a car and it might fall through. im just so overwhelmed and frustrated and i feel so alone, whenever i say anything to my parents they tell me to shut up and deal with it “its being an adult” but ive never made such a big purchase and ive lost sleep over the fact that this may just be one huge mistake and im wasting all the money i made; all the money i spent months crying, not sleeping, not eating, not socializing, and letting myself be abused for.