It is very unlikely that different bulbs would be causing this problem, unless you installed something very radical. Even then, if they were working but now keep blowing fuses immediately, that isn't likely your source of grief.
The relay that turns on your brake lights is in the fuse block under the rear seats. It derives power to turn them on from that same block.
Do you have any problems with other lights? For example, if you have your headlights turned on, do your marker lights work? What about your signals / hazard lights?
If it is a wiring issue, it will be somewhere between the fuse block under the rear seat and the tail lights. Inspect all the wiring very closely. You may have to take the trim carpeting out of the trunk to access everything. Also, take your tail lights off, remove the bulbs and inspect both the bulbs and the sockets carefully. When you replace the fuse, is it okay until you step on the brake pedal the first time, or does it blow as soon as you plug in the new fuse?
Please be sure to answer ALL the questions I've asked