Support to bring my children back home

Im a young mum 3 children my oldest lives with her dad. my other two childern who are now in foster care. my 3 year old son was living with me up untill January 2015 i wasnt coping very well and had a drink and drug problem so I asked children's services for help I'm signed my son over on a section 20 act I've been clean  for well over a year and have been having regular drug tests twice a week and once weekly i attended addaction of my own accord seeking help for my problem all test have negative results I also attend Alcoholic Anonymous and Narcotics Anonymous meetings I have contact with my son twice a week and has been promised by social services time and time again that my son would be returned home to me I have had endless parenting assessments and all that can out of the parenting assessments is that i needed help with childhood illnesses which I got help with a community health nurse. Since that children's services are now saying my depression and anxiety is a problem for me looking after my children and I'm not capable. also my little girl who is 4 and a half months old I gave up on a section 20 act again recently on the 28th of February  2017 of because I felt pushed by social services to do so as they were threatening me to take my little girl away through court so I thought by doing a section 20 act would help with my case of getting my son back also help me prove to Social Services I can cope with two children as they were saying I can't cope with two children being a single mum and not having any support but I do have support I have my friends and family social services even set up a meeting to see what support I had and we arranged a plan of what my friends and family would do to help me when my children would return home but again this plan was never put into place I've done no endless contact centres I was having contact with my son in my home unsupervised with my little girl at home too and now social services has taken my section 20 away so now the local authorities have full care and power over my children. I can't see any of my children at our home anymore I have to see both children back in a contact centre also children's services on now trying to adopt my children out after I've done everything they have asked me to do and more. I am not a bad mum I put my children first befor my own needs and to keep them safe so i asked children's services for help.  as I wasn't coping at the beginning of January 2015 and wasnt in a good  place at the time. I put him first before myself and I've done all I can to try and get him back. my daughter has recently lost her father in a tragic car accident so all she has left now is her mother and i so wont her back to give her the best in life with her mummy and her little brother who ive been trying to fright to get him living back home with me for last two years now :(