Joe,
Some of us are not as gifted athletically as other people are. You have to find what you are good at and play to your strengths. As an off-ball or crease attackman, there are two things that are very important.

The first is that you have to know how to get open. Never stop moving and try to anticipate two passes ahead. If the ball is on one side of the field, the open area will likely be a cut to the weak side as the ball moves. Also, if you see the back of your defender's helmet, where the writing is, he cannot see you and that is a great time to cut.

The second key is making the most of the few opportunities you have. Working on your shooting, especially placement for an inside player, and cacthing the ball behind your head for a quick release will help this. I hope this helps and I wish you the best of luck.