There are lots of "due date" clubs, and a few older parents clubs, but I haven't found one for younger parents yet. Honestly I'm not sure how you want to define young mums... whether it's under 25, under 21, under 20... either way, if you consider yourself a young mum, maybe we can all chat here? :)
I'm 19 and due end of April/start of May. About to start 2nd year of university, living with my other half and this was very much unplanned.