it could be multiple things. poorly funtioning glutes, tight hip flexors, tight hamstrings, lack of strength in your lower traps ect. it is probably a combination of these things actually. just because you have pain in an area does not mean that that is the problem area...it could be that your real problem manifests itself in your back. knowing that you are in school, i would bet you sit a lot right now right?
the problem with lots of sitting (now and in the future in your career) is that your hip flexors will become tight (and even shortened), and your glutes will not function very well from lack of activation.
can you take a picture of yourself shirtless from the side, front and back. make sure it's from the knees up. that would help a lot.
right off the bat i would suggest doing this before your workouts:
foam roll your hip flexors, IT Band, glutes, hamstrings (you can use a medicine ball or tennis ball instead if you dont have access to one)
30 second hip flexor stretch on right leg, then 30 sec on left leg, followed by 10 glute bridge ups (squeezing your glutes and pause at the top of the ROM)
3-4 sets of each.
also2x/wk 2 sets of 15 reps each direction of lateral band walks: (
http://www.ronjones.org/Coach&Train/BodyXerciseLibrary/Alternative/Bands-LateralWalk.html )