Thanks Mysinking I feel so much lighter since reading your post. You're right he doesn't deserve me noticing his texts. I love this thread 
Crystal it's hard to explain the truth to DCs, but I think you should continue to try, as you've done nothing wrong. It's the situation not you 
Perhaps you could talk in terms of explaining that you have an amount of money every month that needs to cover lots of things and that you need to keep some for Christmas?
With a 13 year old I would say that child maintenance has stopped too I've been straight with my 10 yr old on this , but I can understand if you think that could cause worry. Beyond your useless WN, it sounds like your pregnancy is going well, you sound strong, and your DCs will have the excitement of a baby about within 2 months 
Biblio and green my poor ex has really suffered since we split, poor little victim is completely looked after and poor little victim does completely as he wants, but is still a poor, poor victim. Let's all feel sorry not for these men who get everything their own way and it's still not enough.