My vauxhall astra estate mk4 1.7 dti has conked out.please can any1 help me?

hi please please can any1 help....my vauxhall astra mark4 estate 1.7l dti has been slow starting for about 2 weeks,and yesterday after dropping my daughter 2 school it cut out completly.when i tried 2 start it it took a while,then cut out about 3 miles down the road.it was having trouble starting,and the battery became completely dead..my brother came and towed me back..we charged the battery for a while,then i took it round the block twice and it seemed good to go.went and picked my daughter up 2day and coming back it broke down again...it started after a while,then after a short while later it broke down again...the battery has gone completely dead again and i have left it by the roadside.only 2 weeks ago i had to buy a brand new alternator because i was told it was stopping because i needed a new alternator...which doesnt seem the case?! so if there is any1 that can help me id be so grateful....thanx