I accidentally enabled firewall in my Ec2 instance which blocked me from SSHing --> Then, I used this answer to https://stackoverflow.com/a/50999373/3705478 gain access to my Ec2 instance, but my public Ip address changed. --> This caused me to update my Ip address with Domain registrar as it is a web server facing public. Also I have to change the ip address of the DB running Ec2 instances.
How can I prevent my public Ip address changing under such situations in Amazon EC2?