Is it possible that high dhea levels be causing me to retain water and gain weight?

Maybe yes: Women or girls with elevated dhea levels may have a hormonal problem that causes symptoms such as weight gain, increased body hair, acne, irregular periods, etc... A visit to the doctor for an evaluation and blood tests can tell if the hormones are out of balance.

Probably not: DHEA is not a very reliable test by itself as the DHEA-S is more accurate for adrenal androgen assessment but without knowing what other symptoms you had which made your doctor order it it is hard to know what is going on. For regular periods and/or increased facial hair, a high testosterone level would be more meaningful but even then wold not explain weight gain