Ouch!

Just to give you some context. After 20 years I decided to get back in to archery. I'm 54, 195 lbs and in great shape, I hit the gym 3-4 days a week and not to brag, I can still bench press 270....But!, when I pull my 55lb draw compound bow back my shoulder is killing me! I can target practice about 18 shots before I have to quit. Is this normal?........Do I just need to strengthen those muscles with practice?