How did I know it was the Haberman? Because when we got the all clear to try regular bottles post-op (he was unable to eat from a regular bottle pre-surgery) he wasn't sucking. He chomped. It was a distinct action different than nursing or sucking. I tried to nurse him, and he chomped there too. I felt in his mouth, and he didn't bring his tongue up and around but chomped away. That is how cleft babies learn to get milk out of the Haberman, as any motion with the mouth will get milk out, and he had had to use a Habermand with the slit turned to the easy position.
In your situation, I would probably start backing away from bottles and try to nurse as much as possible.
The moms who are struggling are the ones who come looking for help, so probably 95-99% of us here had some sort of problem with nursing at least one of our children. When I started nursing, the forums didn't exist, or I'd have found my way here then (I went to a IRL LLL meeting). The ladies here kept me sane through my fourth son's first year and onward with his birth defect when we found he couldn't nurse and I had to EP.