Implant too large?

I am 5'7" tall, about 150 lbs and previously a 38B cup.  Had single mastectomy in January 2014, with a tissue expander filled to 410cc.  Exchange occurred in July 2014 with a Natrelle 410 Highly Cohesive Anatomically Silicone 740cc.  I was surprised to wake up to a 740cc size implant and it felt too large.  It has been over two months and it still feels too large although it doesn't look too big.  Mostly pain issues in my shoulder and arm but also a tight chest.  My option is to go back for a smaller implant.  I am not a big fan of another surgery but would like to see if anyone else has faced this decision.  Not certain I can live with this size.