Babies definitely ebb and flow. My daughter was sleeping 5-6 hours from about 7 weeks until probably around the same time. And then it changed as well. It's important to stick with a routine they can depend on and become accustom to. At 3 months she is still very, very young but by sticking with the routine and making minor changes as needed baby learns what to expect and what is expected. My son would go thru periods where he would be wildly different for up to 6 weeks and then things would go back to normal. Just part of parenting. Stay with a consistent routine.
It's important to remember that babies have to learn and be taught how to sleep. They don't automatically know how. Around the 3 month mark they begin to start gaining a better understanding of this big world they are in and it's a good time to start routines. They may not get it for a few months but it's part of the learning process for good sleep habits.
Just a word of caution regarding Babywise methods-the author is not a medical doctor and has zero medical training. This method is very controversial and has been known to cause failure to thrive in babies.
I was able to learn a lot and glean very valuable information from Dr. Sears Baby Sleep Book and the Baby Whisperer. I didn't use either of their methods exclusively but created a routine that worked for us.
Also note that if you are breastfeeding you will have times where baby wakes more at night. Just part of parenting at night. :)