Help with staight ball bowling.....?

I am a straight ball bowler. I throw from the far left dot and hit the head pin. I bowled really well pregnant, a 200 game. But now that I am not pregnant everything is out of whack. I have the same approach. One time I will strike, one time it will go perfectly straight and hit 1 pin, one time it will cross over all the way and hit one pin. I have tried slowing down my approach, but that does not seem to help. I am looking for tips.