I wrote my reply earlier and now I see that Monique has replied. I will probably repeat a lot of what she said but I hope that helps to confirm our support.
The short answer to you is a definite ‘No’ – you are not a terrible person if you leave, however, I would never suggest you either leave or stay – that decision ultimately has to be yours.
I am going to bring up a thread I wrote some time ago ‘The F&F Cycle’ which I hope will help you understand the confusing life you have been living since you moved.
Your fiancé did not ask for or want his addiction any more than you but you cannot make him stop gambling – only he can do that.
Whatever you decide to do I think it would be good if you could print off the gamblers anonymous-20 questions which you can find in our ‘Resources’ at the top of this page. Click on the first paragraph – ‘a comprehensive online support service’ and then type 20 questions in the ‘search by keyboard’ box. Click on Gamblers Anonymous – 20 questions World and then follow the link. If you tick the boxes that you would say he should say ‘yes’ to then you will know that you are living with an addiction that will get worse without acceptance and treatment, if you give your fiancé a copy then perhaps he will begin to see that he has a recognised problem but that he can change his life.. Perhaps you could find a group of GA (gamblers anonymous) for him to attend but never feel that you have to hang on or save him – his addiction sadly will use you even though he is not deliberately hurting you.
It is great that your mum is there for you but sometimes those who care for those who love CGs (compulsive gamblers) do not understand.. The addiction to gamble divides families feeding on lies and secrecy and unfortunately unless people have lived with the addiction, their opinions can be very narrow and not supportive so personally I think it is best to say things as a statement rather than asking for opinions. You can gather information here so that you can make your own informed decisions with that knowledge but it is better to share – especially as your fiancé’s addiction is endangering your future.
I think that is enough for me to start with but please write again. The support and understanding is here for you and there will never be any judgement regardless of what you finally decide.
It would be great to meet you in a group where we could communicate in real time.