my baby gets fussy at nights before she goes to sleep!!

my baby is 9 weeks and she is pretty well behave baby. I mean, she gets fussy just when she is hungry but lately at nights she is getting fussy when is time to sleep, she wants to be held to fall asleep. sincerely my back hurts so much , every day the pain gets worst, I don't know what can I do to make her sleep without being held for 30 min until she falls asleep. this happens just at nights. when she finally falls asleep, she sleeps for 6 to 7 hours straight. what technique can I use so she falls asleep faster without being held?? thanks !!