Why my ec2 instance works for some time and then goes down?

[kartmycity]

I have a ec2 t2 small instance and i am using Cloudflare for dns.I have whitelisted all Cloudflare IP’s in security group. My problem is my site works for sometime when i work in backend testing and configuring plugins but when i log out and try to reach my site it gives 522 then suddenly changes to 502 error. when i see in console in volume my burst balance shows Zero I dont know why it keeps falling to zero when i work for sometime, but when i stop my instance for few hours and come back do some work then again same thing happens. where might be the problem? I tried: Reinstalling wp downgraded to lower version of wp disabled all plugins