single parenting ASD teen and siblings - financial chaos...

hi, i'm Lisa and I've just got back from a really useful meeting organised by NAS surrey about transition.

my question is about my financial situation. 

until 6 months ago i was in a long term (20 year) relationship with the father of my 4 children and we took care of all of our children's needs.

since he left i have found myself in financial chaos through no fault of my own and am trying to secure the future for my kids, especially my 19 year old with ASD.

i was turned down for pip, am not eligible for a carers allowance, but was told i should apply for ESA  but after going on the site i'm utterly confused and have gone around in several circles.

i'm a full time teacher, but am eligible for child and working tax credits  they even sent me a 'free NHS' certificate - so clearly things aren't great. 

my question is, how on earth do i get more financial help for my son knowing that he is unlikely to become financially independent anytime soon.

i consider myself to be fiercely independent and pretty bright but this system has me flummoxed 

any help or advice about this or anything else would be greatly received  

i see a solicitor tomorrow and hope they can help too..... 

thank you