I think that I might be bringing you bad news. I've just been reading the requirements for becoming a midwife, here:
http://www.learndirect-advice.co.uk/helpwithyourcareer/j obprofiles/profiles/profile326/
It seems unlikely that, without any relevant qualifications, you'll be able to move into this type of work.
There might be a small ray of hope, though. There is a reference, in that link which I've just given, to gaining NVQs through working as a health care assistant. Although the Learn Dircet site (from which these links are taken) regards the jobs of 'care assistant' and 'health care assistant' as different roles, there is clearly a good deal of overlap with what you're currently doing.
You might be able to get employment as a health care assist within a hospital (ideally, a maternity hospital) and progress from there. Here's the link for the job of health care assistant:
http://www.learndirect-advice.co.uk/helpwithyourcareer/j obprofiles/profiles/profile193/
Chris