1. I brushed my teeth as I took a shower.
2. I brushed my teeth because I took a shower.
3. I brushed my teeth while I took a shower.
4. I brushed my teeth taking a shower.
(Does #1 mean #2 or #3? Is #3 the same as #4?)
1 and 3 are correct.
Neither 2 nor 4 make much sense. (Your teeth aren't taking a shower.)