I'm 24, no kids, had mirena (levonorgestrel) inserted 1wk ago. still having severe pelvic & back pain daily. having us next week to check, if ok will pain stop soon?

Not necessarily: I'm sorry I can't be more positive. A small percentage of women simply don't tolerate the Mirena (levonorgestrel). Possible explanations may be malposition (which the US should see), a small uterus (may not be apparent on US), and infection (watch for fever and discharge and increasing pain). If everything checks out but the pain persists, you might try Skyla which is slightly smaller.