If your car is a manual there is one other thing to try. Open up the battery so u can see the fluid levels. Get someone to get into the car. Put the car in gear, hand brake on, foot on the foot brake, keep your foot off the clutch and try to start the car. As the car is in gear and the starter is trying to turn the engine it will put a lot of strain on the battery for a few seconds. If u see any bubbling coming from the battery it is going to need replaced. I know its a bit of a drastic way to check a battery but it is easy way to do it if u dont have a tester. Failing that am sure if u take it to a garage they will happily check your battery for u.
please note to be care full if u try first method not to get run over, only turn ignition key for a couple of seconds.
If your car is an Auto u will need to get battery tested