4 month old/sleep regression?

I have wonderful 16 week old daughter. From about 7 weeks to 12 weeks, she went down at about 8pm, woke at about 3am to feed, then woke at 5am to feed again, and down until approx 7. This was great! I loved it! From about 12ish weeks (till present) she has started waking at 11, 2, 5, etc.... Does anyone have a similar situation? Advice? Why the regression?! She is exclusively fed. Thank you!!!!!!!!!!