His nipples begin to tingle as the areolas grow a bit larger. They become rather sensitive under his shirt. His shirt rubbing against his nipples causes them to poke out a bit, tenting his shirt. He suddenly realizes that it isnt just his nipples that are causing his shirt to stick out, but his "pecks" as well. They had grown soft and were beginning to expand outward starting at A cup breasts and slowly moving into B cups. He stood there, eyes wide and mouth open, shocked at this girlfriend had done that to him. While his mouth was open, she quickly shoved two more breast chocolates into his mouth, causing his breasts to swell two more cup sizes.
Around this time was when his crotch started to tingle a bit. The feeling caused him to grow aroused. His hard on stuck out of his pants, but it also made it rather obvious that his dick was shrinking as well. It quickly shrunk into nothing more then a nub as his balls got sucked up inside of him, forming a hole in their place. Female lips pulled around his new clit and hole.
The sensation of his nipples rubbing against his shirt was starting to be too much as he began to grow wet between the legs. Other then the breasts and his lack of manhood, nothing else about his body had changed yet though. He still had, mostly, the body of a guy. He quickly pulled off his shirt, letting his D cup breasts bounce out. They were firm and perky.
"Rach... Why.. Why did you do.. ung"
As he was speaking, Rachel and reached out and tweaked one of his nipples gently, causing his new sex to grow even wetter. He reached up and cupped both of his breasts, actually likeing the feeling of hands on them.