Oh dear, it sounds like the g/f wants him to be distanced from you for her security, sad for the children as this sort of competition normally effects them negatively.
I think you are going to have to have a good cry and accept that you will not be able to parent the children together again as you have the past two years, and that there is someone pulling is strings, which now means there are three parenting your children!
I would not be surprised if she had a hand in composing the text!
At the end of the day I feel sorry for women like that, who feel so threatned about their relationship they would push two parents apart that from the sounds of it were talking well for the children.
I would not be surpised if she is the sort to put your ex ahead of her children!
I hope that the next time you see your ex that you can have an adult conversation with im and you both the two parents keep control of your children and don't allow him and her to dictate to you how things will it, it is so damaging for children!
I don't know what to say regarding you still loving your ex. I still to this day feel sad that the ex and I have no relationship regarding the children, I find it very hard emotionally to deal with so many challenges in life other than the single parent thing, and to have the children's father care for them would be lovely, sadly it is not just the children who loose out it is his loss too!