I know someone who was in your position, I had direct involvement from part of the way through her experience.
She was early 20's and had been in denial about the pregnancy, she had concealed the pregnancy and lied to everyone about it other than her best friend.
At the hospital she signed the S20 and went home. She had no support, and struggled to cope with her decision, a week late she had an emotional break down and was taken to her GP who diagnosed her as depressed.
She decided she needed to see the baby and it was sorted out within a few days, but she had to find her own way to the contact centre in a village 40 miles and four busses away.
She knew straight away that she had made a mistake but she felt that the foster mother tried to convince her her that she was doing the right thing for the baby and it would have an amazing 'stable' life and she was being very responsible by doing what was best for him.
She told the SW that she wanted her baby back but was practically ignored for over a week because they didn't think she was 'serious'.
Then when she put her food down and told them she wanted to take her baby home they agreed but insisted to jump through hoops such as multiple home visits to check she had a long list of items that she 'needed', the sw insisted on witnessing her tell members of her family and friends that she had a baby, but insisted it should be done one on one at different times, so it took a long time to get through everyone on the SW's list, even though most already knew by then.
she was also told that she had to learn how to change, bath a feed the baby, and show them that she could do it, over and over again.
They also insisted she complete other unnecessary assessments and tasks.
After jumping through their hoops for four weeks she had a meeting with the foster mother and the SW to discuss taking the baby home, but the SW and FM discussed it and agreed that she wasn't ready and the baby should stay with the FM for a little longer, their reason was that they didn't feel she had bonded well enough with the baby yet and they wanted her to continue with the visits for a little longer.
She she had to make the 6 hour round trip by busses every other day for a one hour visit.
After eight weeks they had another appointment, this time the SW's supervisor was present, I was also present as support for the mum.
Again the SW and the FM did all the talking and decided that they didn't think she was ready to take the baby home yet, the FM seemed especially insistent that she thought it would be a mistake for the baby to go home yet.
The mum looked heartbroken and I was worried she would agree, but she had clearly had enough, she turned to the supervised and told him that she had done everything asked of her and she just wanted to take her baby home, she begged him to give her a chance.
Then one of the most shocking things I have ever experienced happened, the supervisor told her that if she felt she was ready it was her choice to take her baby home. He was only there under a voluntary care order (a section 20), at her request, and she was free to take him home whenever she wanted.
It turned out that she could have taken him home on that first day, they had just been stringing her along and lying to her for no reason for two months!
In my profession I have seen a lot, but that was something that will always stay with me, I just couldn't believe they would behave like that.
There was never any explanation as to why they did it, but three years on the mum and her son are doing fantastically and SS had no more contact once she had gone home other than a couple of 'check ups' just to see how they were doing.
It sounds very much like they are trying to do a similar thing to you Bright, please don't let them.
You have every right to change your mind about the voluntary care order and collect your son any time you want.
Of course SS will want to check you are able to take care of him but there is no reason why you can't have you baby home immediately.