12 week-ish babies can be notoriously hard to settle - they are becoming much more aware of what is going on around them and also growing rapidly. It's very very normal!

Things to try that may help:
1) Less caffeine for you if you are breastfeeding - caffeine "wears" off for an adult in a few hours, but takes a couple of days for a baby to process.
1a) If you are breastfeeding then make sure you offer both breasts now - she's growing and may be hungrier than she used to be. It's also OK to feed her more frequently, and doing so will help your body make more milk for her.
2) Take her for a walk outside - the different noises seem to be calming for lots of babies
3) Give her a bath - it is OK to bath a baby at 4 in the morning if it helps them sleep!
4) If she seems to have a bit of a sore tummy then rub her tummy or lie her on her tummy on your tummy to help her burp and let off and feel better
5) Put on your favorite music while she's grumpy - it may make you feel a bit better and that's got to help

Babies change all the time - and what works now probably won't work in a few months. That's part of the fun!

hugs
Kate