Hi,I'm j-1 visa holder and I wanted to know if it is possible to change if I have 20 days to the ending of my DS-2019:)

Change from J-1 to??

First of all, which group of J-1 you're in? Certain group of J-1 holders are subject to two years in home country. So you may or may not be eligible to file a change of status.

Normally if you want to apply for change of status to any non-immigrant visa, you should submit the application between 60-90 days before I-94 expires. If you don't receive any result from USCIS, better leave or your record will show as "overstay".