Shoulder pain when serving!!


I just started playing tennis about 1 year ago (I'm 23), I play 4 or 5 days a week during summer, once or twice at the club during winter.
I play decent, I like staying at the base line hitting the ball with a lot of power using a semi-western grip.
I've improved my game overall, BUT my main problem is my serve. Everytime I want to serve using the continental grip, my shoulder hurts. Whenever I'm trying to twist the shoulder, when getting close to impact the ball, I feel like my arm does not turn all the way so the raquet faces more sided instead of forward, making the ball fly away with not direction (most of the times it just goes to my left side, I'm right handed), no power, no nothing, plus I leave the court on pain.
So what I've been doing is serving using the semi-western grip, which does not required that much arm rotation. I can serve with good direction and good power using that grip, but I know it's not the right way!, but then when I wanna practice with continental I go back to balls flying everywhere and shoulder pain.
Is it just beacuse I'm not used to that grip and it just feels so weird?, will the pain disappear once I get used to it?, and... I think I know the answer but, are there any pros out there that don't use a continental grip to serve?