Taillight issue

So, before I go blindlessly digging around to try and fix my problem, I figured I should ask here first to see if anyone has encountered the same problem as me and what they did to fix it. So my problem: my taillights(the running lights when headlights and/or markers are on) stopped working, but The brake lights come on if I press the brakes. So the brake lights work but the running lights don't. Here's the weird-er thing…if I don't have any lights on at all and then press the brake pedal, the driving lights come on(along with the brake lights). Sounds like a short to power maybe? I found the purple box to be not good and replaced it. This fixed everything for about a week…then blew again. So that would mean high amperage and a possible short to power somewhere, yes? Any help in where I should start looking would be appreciated