@tanja1101 Hello there, thank you for coming to the forum and sharing your situation. I appreciate this is a challenging time for you and your son, as you have both had a lot of change to cope with, and when our children are young, they can find a change in circumstance very tough. So, here are a few suggestions for you that may or may not work for you, but it's a start.
1. Recognise and realise that it's ok for your son to be displaying his emotions. He will be looking to you to gauge your reactions and to see how you deal with them. It is up to you as his parent to let him know and to teach him what is an acceptable response to these emotions, so for example - him screaming and hitting is not an appropriate response, so try to show him other ways of expressing himself. There are some great free, online resources under the title of "emotions and expressing them with children" that can assist you with this. Using different faces and talking about them, asking him which face he feels at the time he is crying. It sounds obvious, but as parents it is vital that we listen and read our children's body language to better understand why they are behaving like they are.
2. Be reassuring towards him at every opportunity. He needs to know you are not going to leave him - even if that is you just popping upstairs for a moment. Talk through where you are going and reassure him that you will return. For times like these around the home, if you can, perhaps set a timer and say "Daddy is just going upstairs. When the buzzer goes off I will come and see you." Give him praise and encouragement when he lets you go for a couple of minutes, to begin with. Expect nothing, praise the small victories and then gradually you will be able to be apart for longer.
3. Make a point of scheduling into your days when you are with your son, a period of 1-1 time - this is a period of time where your son will get to choose what activity you and him can do together. Make it no cost - so playing with Lego or cars for example, but you let your son lead the playtime. Encourage and praise him for good play time and you will hopefully see a change in his behaviour and he will be better at playing on his own, because you have spent this dedicated time with him. This should be about 20-25 mins for a four year old as their attention span is shorter.
4. Is there any way that when you are with your son, that your work calls could be more flexible? I understand working from home can be tricky when looking after a young child, but for two days a week is there any flexibility?
5. Each time you leave him with Mum, leave him with something to look forward to for your next time together. Reassure him that you will see him soon, and try to not be shy in telling him you love him. Has he a special bear he could leave with you to be looked after by you? This way it will be there for when he comes and stays at your home.
6. I'm sure you are aware of this, but try to be positive about his Mum, and perhaps do a craft activity together so he can give her a gift that he has made whilst being with you?
7. Finally, you'll be pleased to read!, when your son is having a meltdown that involves screaming and being angry and crying, if you are in a safe place, ignore the behaviour as much as you can and say to him "Daddy will talk to you when you have calmed down." It may take a couple of times, but you cannot reason with a child that is in the middle of tears etc.
So, if the above is too much to take in remember : Reassurance, quality playtime, look forward together, ignore negative behaviour, and praise and encourage and reward good behaviour.
Wishing you and your son all the best,
Fegans Parent Support.