Multiwan not working because of nat

[Wisynet]

Hello everyone.
First of all sorry for my bad english. I am trying to make a multiwan connexion. I'm receiving from my ISP two different internet connexion but the ISP is natting the both IP adresses. So I receive for each connection this configuration:
IP : 192.168.1.2
Mask: 255.255.255.0
Gateway : 192.168.1.1
DNS:192.168.1.1
On the both ADSL line I receive this configuration. I have to pay more money to have access to an Public adress.
When I'm trying to make multiwan It is not working because it says that I'm using the same gateway on the two connexions. I want to know if there is a way to convert one of those IP adresse to something else so I can do the  multiwan loadbalancing. Public adresses are too expensive in my country and I can't pay for them. I try to use virtual IP but I don't know if it can resolve my problem and I don't understand realy how it is working.
Please if you have an idea of how I can figure it out, it will be very helpful.
Thanks to you

[costasppc]

Change the routers (at least one of them) LAN address/network.

You can use 192.168.1.x to the one and 192.168.2.x to the other one.

Your pfsense LAN address/network must be in another range as well.

So:
pfsense: 192.168.0.x/24
Router 1: 192.168.1.x/24
Router 2: 192.168.2.x/24

Best regards

Kostas