I am a 21 year old, 200lb man, i just drank 20 ml of delsym (dextromethorphan) (30mg per 5 ml) and i need to know if i should do something or if i'll be ok?

Should be fine: But you could hallucinate and be groggy. I would just go to bed and not operate anything more difficult than the water dispenser on the fridge. Drink a couple glasses of water to make sure you are well hydrated, so you don't feel like a slug tomorrow. More doesn't necessarily mean more effective. And do not do cough meds for entertainment.

DOSE IS 10ML/12HOURS: Adult dose of delsyn is 10ml every 12 hours not to exceed 20ml in 24 hours you took double of single dose of delsyn .It may make you little drowsy and you have to be careful while driving etc and drink plenty fluids and do not take the next dose which is due after 12 hours.