I've been struggling and don't know what to do

So I (16M) have been struggling a lot with my mental health for a year or so at least now, and recently my mental health has been taking a major hit due to my mum's own problems (mostly suicidal related issues and Bipolar related problems) I am currently seeking mental health support through therapy however atm I cannot visit a walk in centre due to my younger sister still attending school, I am potentially going to visit this coming Thursday, however until then I am remaining unsupported and even then the visiting the walk in centre, so I may remain unsupported for a long time, and I just really need some help. (I am UK based if anyone is going to recommend support groups/companies)