My phone isnt charging! Help!

So my phone was left on 2% and i got the 30 sec message from the phone i put it to charge and i forgot about it but when i came back it was still at 2% and after 1 hour of trying to figure out what is going on it went to 0% and when i tried to charge it it automatically turned on (which didnt happen when the phone was charging normally ) and i got it fixed with a new battery and charging port but yestarday the same thing happened can someone tell me what can i do to fix it ?