hi willow, im not sure if i can help you, but similar happend to me i left school with 2 grade c's and above, had little help at home, i lived with my grandparents who threw me out not long after, i am now 28, and am an architect, i achieved this alone, with no help from family, starting with a gnvq construction course in college. gnvq's are available in hundreds of subjects, engineering, nursing, science, travel and tourism etc, and start at foundation level, (no gcse's required to enrol) i started on the intermediate level. which you should too. you can also re-take your gcse's which will fit into your timetable, i worked in a local bar to support myself most nights but was well worth the struggle. my so called mates used to tease me back then, and i now earn three times what they do now.
so its not the end of the world, just try to figure out what you want to do, and im sure you'll achieve it, good luck
wil