phone battery and charging port

My phone has a battery problem. It tends to increase without being connected to charger and sometimes decrease when connected to a charger (without use). And today, after i charged my phone to 50%, I decided to power off it to save the battery so that i can use it later. However, I could not switch on my phone anymore. The screen is always pitch black no matter how many times I press the power button, or press the volume buttons then press the power button. i searched some tips online which advised me to charge my phone for 1 hour and see what happens, but my phone's charging port is quite lose and it usually takes a lot of effort for it to finally charge, and now since the screen is totally black, I dont know whether it is charging or not. its been more than 1 hour, and nothing's happening. The screen is still pitch black with no response given. Please help.