Alina, I know exactly what you're talking about. I went YEARS just assuming that because of the way my collarbones are I just had to deal with a constantly bruised and, frequently, blistered shoulder and pain down my arm. I mostly tried Gregory and Osprey packs because they felt the best at REI, but once on the trail the same thing would all happen again...
Anyway, I read a lot of good reviews about the humorously large shoulder straps on the Gossamer Gear Gorilla and tried it...and wow what a difference! And you know what? It only really contacts my shoulder in the front. Unlike my other packs where the straps wrapped around my shoulders, the gorilla barely rested on my shoulders, even fully loaded. I initially thought it just didn't fit, but I kept using it on several trips and honestly, I don't care what the shoulder straps LOOK like, I can finally hike without weeping blisters on my bony shoulders!
I bought a ULA circuit to use for the JMT (for the bear can), but I'm still holding out judgement. I had a teeny bit of the arm pain during the first time I took it out but it was fleeting. Ill need to try more trips before I make a final decision.
My long, drawn-out point here is that many of us have a hard time finding a pack that actually FEELS good...but there will be one out there. I understand you don't have the luxury of ordering and returning over and over...but maybe you'll luck out ;)
So don't worry about what it looks like, just take it for some hikes (even in the neighborhood) all loaded up with YOUR gear, and see how it feels. But be prepared to make mistakes...no one can pick a pack for you. Unfortunately........