Seeking expert counseling is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
I believe that I can help you.
You are suffering from Panic Disorder with Agoraphobia, most likely. Agoraphobia often accompanies panic attack and it is a fear of going out so that you are not compromised or helpless or embarrassed if you have an attack while away from the safety of your home.
These attacks can be treated with medication very successfully FOR THE SHORT TERM.
However, you must come to terms with your situation.
You say that you feel safer in the UK than in Sweden, but you have more family support for your son in Sweden.
Sertraline is alright for general anxiety even though it is an antidepressant. If you want to get instant relief from panic you need a benzodiazepine, most likely alprazolam. However this is something you should only take AS NEEDED when you feel these attacks coming on.
You get super-stressed in UK as well and have no support group. Which is worse do you think?
What is your biggest concern? Having someone trustworthy or familiar with your son or staying in UK?
Why do you feel unsafe in Sweden?
And how old is your son?
Could you work that specific job in Sweden as a UK representative? Can you say what the job is?
3.5 is a wonderful age, but he needs close family.
And do you have any supportive siblings, aunt, cousins, grandmother, etc.?
And you can open some doors in Sweden and take your skills with you.
How about some family or friends that love you?
Would she help you?
Can you help her and she help you? Can you do your desktop publishing from long-distance?
Have you spoke with her about your situation?
Could you work together somehow?
They prefer it but could you still do it?
You do not have a full-time job now.
That could be a strong possibility that you should investigate
You have to set your priorities. I'm sure that your son comes first.
Friends in London?
Your son's father?
If you get a full-time job do you have care for your son? That is probably very possible in London. (I used to live in Islington and Oval).
What do you see as your best option, then your second best, and then your third best?
Can you survive part time?
What are your living arrangements now?
By yourself or with flatmates?
Are you with people who can share tasks - i.e. other mothers?
I have spent an hour of my professional work time with you giving you lots of suggestions and listening to your problems. I did NOT give you poor service and do not deserve to be receive the brunt of your frustration and anger. i am still willing to work with you if you wish.