Shoulder pain. Tear? shall i go for mri?

Hi, I have been gyming from past 2 years.from past few days I am having slight pain while working out.last week while I was doing overhead presses my right shoulder just gave up..it has less power as compared to left shoulder..i usually do overhead presses till 20kg dumbbell but with right hand can't go over 7.5 kg now..this is also while doing chest fly..however there is no issues with my movement  like moving my hand up/ down and sideways. Also when I move my right hand forming an L Shape backwards, I hear a popping sound although it's painless.i also feel  slight pain on the top frontal part of my shoulder when I try to keep my right arm behind my back or while doing push-ups?What is the probable cause? Is it an impingement issue or rotator cuff tear? Shall I go for MRI?