Parental Alienation

Hi, I have previously had some great advice so I am hoping you maybe able to help me again.

I am actually a mum that has been going through [censored] with my ex husband for past few years.

All was ok stopped contact overnight we did at the beginning do 50/50, this is when he removed children from my care completely telling me I had to go to court to see my children.

After a long wait court did not award 50/50 but we had a plan and it was working. My son who is 12 has asked before about staying with me more than he does, he stays over every other weekend and then I have him two afternoons after school a week also. I have had no issue saying yes, his dad said no your mum isn't allowed. ( This is not the case) 

Whenever I question my ex husband I get it's what son wants not what you want although what my son wants he has stated clearly ignored by dad.

My Christmas this year my son had his first Christmas with maternal family for a few years had a great time etc, and we have booked a large family holiday within the UK for the summer, I asked my son if he would like to come, Yes he replied, I said I would speak to dad and make arrangements, no he said I will ask, he did and his dad said yes after apparently quizzing him if he really wanted to go or was he being made to go.

Now the behaviour from his dad is becoming unreal, he again has made every excuse on reasons my son can't come after school he hasn't stopped overnight since Christmas, on the one of the very few occasions I've seen him since Christmas, today I have seen him, I asked him are you not stopping over tonight no got to be home at 6:30, why don't you come anymore. His response was exactly the below.

' I want to come but I don't feel comfortable anymore' 

So I asked back what is the problem what makes you feel uncomfortable ' I don't know' can I make some changes 'no' so what is it ' I don't know' 

When my ex husband stopped him seeing me overnight I was weeks away from having a new baby and my son was happy and counting down the days to his new baby brother coming, so happy. I know my ex husband told my son I told him I did not want to see him at the moment and not the truth, cafcass actually gave him a warning message when son starts asking questions when his old enough he will likely turn on dad, the advisor had seen it many times before to dads and mums. As my son has always said through all his interviews I love my mum and want to see my mum. And it ringing alarm bells family holiday happy occasion ex husband can't allow that son may realise which he knows I'm not this person who I have been made out to be.

To top it off my son will not save my mobile phone number in his phone nor will give me his, my ex husband has still not updated school to my details, he requests son is returned home at silly times on his previous weekend stop overs, which removes my ability to have any fun days so to speak, or a relationship with maternal family.

I am petrified of challenging him as when I do he removes contact blaming non contact on colds etc. so If I complain he reacts with not his fault son unwell when his perfectly fine.

My issue is I would go back to court, but soon as those papers land my ex husband will tell my son what to say to the degree it's drummed in, although I cannot prove this but statement I want to stay but I'm not comfortable

He can't say why and the timing I know my ex husband and how he can be

Any advice or where to go? I am sorry for the lengthy post