My Iphone 5 wont charge unless its turned off & the battery percentage keeps changing

So for the past month my iphone 5 has been acting up. First it started that it wouldnt charge, so i simply thought the charger was broke so i bought a new one. Well, that didnt work and still didnt charge my phone till after a while of fiddling with it it finally started charging. Then recently, it completely wont charge, so it finally it died and i just plugged it in to see if it would connect and charge & when i woke up in the morning i turned it on and it was fully charged. & also, since now i can actually use my phone, i noticed the percentage in the cornor keeps changing for example, i look and itll say 8% then two minutes later itll say 12%. Can anyone help me? do i need to just get a new phone or what?