Problems with traps. Fat sitting on top or Muscle imbalance?

Ok, I kind of have a problem and I'm not sure if it's serious or not. Everytime I get into a push up position I look in the mirror with my shirt off and notice that my right trap seems to be bigger than my left. But when I'm standing straight both sides are aligned. I've recently booked an appointment with my doctor to see if I have some problem with my spine, but I highly doubt it since scoliosis doesn't run in my family. Other than that I'm 5'8, Male, and 150LB...and I do admit I'm kind of chubby lol. So, I'm not sure if this is a muscle imbalance or just fat sitting on my one side. I know you can't spot reduce, but I'd like to know if anyone has come across this before. Oh yea, I've also started going to the gym with my brother to get fit, but not entirely sure if it's fat or not. Thanks in advance!