@kimchi1 , the reason for the question "which form" is because form 1040 series is ONLY for citizens/Residents/Resident for tax purposes. 1040-NR is for Non-Resident Aliens. Since you came here in 2013 ( and assuming that you had no earlier visit to the USA for any reason ), you would have been an exempt ( exempt from counting days present ) individual through 12/31/2017. From 2018 Jan 1st. you count days present towards Substantial Presence Test ( SPT) --- so I would have expected that you would have filed form 1040 for the first time in 2018. Is this what you did? Are you trying to amend your 2018 return ? Is your visa still F-1 or was there an adjustment and if so when and to what?
Assuming that you are still on F-1 and that 2018 is the one you are trying to amend and assert treaty benefits and you are here temporarily / no intention to settle down here , -- yes the US-China treaty does indeed allow an exclusion from US taxes for the first $5000 of income -- it does not say for how many years ( just uses something like "reasonable" if I remember correctly ). Yes in such a case you have to file a 1040-X, backed up by form 1040 ( the amended return ) and attach a form 8833 declaring the exclusion amount and treaty name and article # .
Stay safe
pk
