Sleeping pattern

So my lo is 13 weeks so she’s transitioned from newborn to baby and I’m having such a hard time with her sleeping. She’s having like a pattern ! One day she will sleep the whole night then the next she won’t then she will sleep then she won’t . Not sure why she’s doing that she has the same sleeping schedule everyday by 8p-9p I sleep her and have all the lights turned off so she already knows the routine she has me up until 7am when she don’t sleep ! Is awful