i brewed a bavarian hefe and after a week in the bottle i tried one and it tasted really watered down is that lack of carbonation or could it be my beer
It could be either or both, actually. One week in the bottle is not very long, so it may not be fully carbed up yet which would explain the watery taste. Let them sit for 2 more weeks and then try another one; it should be better.
If you post your recipe and process, we might be able to help determine if that is also at fault.