At this stage, you are fixated on the injustice of constantly being lied to. It hurts a lot so you can’t think past that stage. Thinking past it would be looking at making changes to ensure a much better for a good future for yourself. Thinking past it would be preparing to set yourself up for disruption and more hurt now ready for peace and contentment afterwards.
At the same time as being fixated on the injustice being done to you, you are planning to marry him (knowing he is a liar)
Knowing he’s a liar kind of negates your own vows to him doesn’t it and turns you into a liar too by accepting his word as truth when you know from years of experince that his word means nothing.
You are right to feel the injustice of being lied to. Injustice is a terrible emotion, one of the worst to have to deal with. It eats away at you. So I’m sorry you are subjected to it on a daily basis. Never being able to orient yourself within the relationship is torture.
But you are very unreasonable to continue to allow him to cause you that injustice….to treat you so appallingly. One lie should have been enough.
You can’t be with him OP because you will never ever be able to trust his word…whether it’s a little thing or a big thing, his lies make it impossible.
He has already ruined the partnership. it’s already done, unless you continue to condone his lies of the past and his as yet, untold lies of the future.
Decide what your own decent standards and values are. And what your expectations of a husband should be. Then set him straight on them and explain you know he will never be able to meet them .. not even half way because everything revolves around truth which he is incapable of giving you. Tell him you are sorry to say that that means cancelling the wedding and never taking him back as a partner.
Or ……you can go ahead with the wedding knowing your life will be even more miserable than it is now and being unable to complain because you knew full well the kind of life you were inviting in for yourself. (and your children if you have any)
One last thing OP, it’s a heck of a job to unravel the causes for compulsive lying. And then to break the habit and then to set new standards and then to stick to them. It will take a life time for him to achieve it even if the will is there to do it.
Your good will can’t do it for him.
His mum isn’t helping him (though she thinks she is) as she is emotionally involved and may even have been part of the problem originally….how sad!