Maternity pay in UK

I'm really stressed at the moment. Iv been graduated from uni for quite a while now and finally managed to get an NHS job interview next week. Basicly in a few weeks im going on holiday and me and my fiancee are trying for a baby on holiday. Iv had an NHS job interview before and they ring you on the day of the interview & let you know if you've got the job or not. My worry is what if they offer me the job and when I get back I go to start work and I have gotten pregnant on holiday? Will I still be entitled to maternity pay still when I go on maternity leave? Iv been reading that you have to work for the employer for a certain amount of time before you are entitled to anything. I'm just really worried because I'm in a minimum wage job at the moment that iv worked for about a year now so I will defo get maternity pay but it won't be very good and don't want to leave to go to a better job to not even be entitled to anything. I just want what's best for my future and family. Any advice anyone? Tia x