Since I found this thread quite easily and since it's not cluttered with any "debugging" I want to add how I solved this issue. I got some grey hairs with compiling the drivers but there are enough good tutorials about that (none actually worked for me 100% but I managed to "compile" a working set from parts of each that worked ..but I digress)

My "driver not loaded" problem was because every possible guide in the internet told me to put the drivers into "qt\4.x.x\src\plugins\sqldrivers" folder when they in the end had to go to "qt\desktop\qt\4.x.x\mingw\plugins\sqldrivers"

Putting the compiled driver files there solved the issue for me and I was able to connect. Hope someone finds this helpful.

edit: also apologies if this thread now bumps up inconveniently