UK, Ireland / Maternity and benefits in Scotland [16]

I have been living in Scotland for 2 years now and have been working for the same company for 8 months. I am 5 months pregnant and wish to go on maternity leave. However I have been asked to get a home office number. I did not know I had to apply for the Workers Registration Scheme but am trying to do so now to claim for my benefits. My employer is unhappy as they had asked me in the past but I did not think I had to apply before and is concerned that I am not working legally and they will now be fined. I have been receiving payslips for the last 8months and paying tax so I should be working legally. Has anyone else been in similar situation and can give advice.