You are welcome. 
Let me draw you a diagram:
PC 192.168.1.x ---- 192.168.1.1 Router 192.168.70.x — 192.168.70.(1?) ISP Router Public IP — Net
Anything starting with 192.168.1 is a local LAN address, never visible on the Net.
192.168.70.x is the router’s supposedly public address, obtained from your ISP’s router. And therein lies the problem: CGNAT. Your ISP hides your router’s WAN IP from the net, so your port forwarding cannot work.
Your public IP has changed, because that’s what public IPs do, unless you pay your ISP for a static address. You don’t need that.
What you do need is for your router’s public IP to be visible. You have to contact your ISP and ask them to turn off CGNAT. Most likely the call centre monkeys you get to speak with will have no idea what you are talking about. In that case tell them you want to be able to access your security camera from outside. Worked for me here in Thailand.
Good luck! Almost there.