why have my braces made all my front teeth move forward?!

i had my braces put on just over 6 weeks ago, and they've been fine, i really like them since my teeth were just awful before, they've moved so much as well. however on 3 days ago i had them tightened, new wires etc..and in 3 days my entire top teeth have moved forward, i do have a bad overbite which i was told i just had to deal with since i hated wearing the block brace, but now when i bite together i look like bugs bunny...? any suggestions why this had happened?