PLEASE LET ME KNOW IF THIS IS THE WRONG GROUP!

So I'm in the UK and I am currently working for an agency, I get regular work but since they don't have a maternity package- I am just wondering what kind of benefits would I be entitled to claim? I work 35+ hrs a week currently and my partner works 40 hours. It would be our first child together.. any help or advice would be much appreciated! We both pay our taxes and national insurance ect so it seems wrong that I don't get any maternity pay when there's others who have never worked a day and not paid any tax or NI and seem to be living better off their benefits?!