172 not starting!!

[sum-dj]

Had it about 4 months, struggled starting quite a few times n wouldn't start at all a few weeks ago. Pushed car up a hill so I could roll downn bump it but it started just before I tried bumping it. Now sat in it and it won't start again. Turning over at first but think battery dead now. Where my mileage is, it was showing ------oil------- where it usually says oil ok. Red light on dash going off when I turn key. Only had oil changed in July so surely can't be that?

 

[Sam@NP]

Checked the oil on the dipstick?

Flat battery.

 

[sum-dj]

Recovery guy said when battery level drops below a certain voltage, the ecu doesn't recognise the chip in the key n the immobiliser doesn't turn off? Says its cos I do a lot of short journeys. So yeah, need a new battery. Cheers.