Hi trinapiano,
Here are a few helpful suggestions for you:
1. You mention technique. Question: Are you able to play now ALL scales, major and harmonic minor, throughout the Circle of 5ths? And arpeggios as well? If the answer is "no", you need to start learning them immediately, both hands in parallel, four octaves, until someone can call out "B flat minor", and you can automatically play that scale with evenness, as well as the next scale called out. Same with arpeggios. Scales and arpeggios are the most essential building blocks for developing technique. If you need to start somewhere, that's it. If you don't have a scale book at home, get Hanon's "The Virtuoso Pianist". The scales, as I recall, are in Part III. His fingerings are excellent and will serve you well for a lifetime. Get the scales and arpeggios memorized. Then, learning the patterns of cadences is necessary as well. Technique is never an end in itself. It is merely the essential means to artful performance.
2. Teachers. Are you in a fairly urban or suburban area where there is a good choice of teachers, especially high intermediate to advanced levels? Or are you in a rural area where the choice is very limited? If you passed a certification exam at a certain level of proficiency, then most experienced, effective and successful teaches would be delighted to take you into their studios. The fact that they are reluctant when you inquire tells me that they are not up to the task, so you are better off not studying with them anyway. They cannot teach you much. It might be that they specialize in teaching beginners. You don't need another teacher saying "Go on to the next piece" or "Use pedal" with no explanations. You've already been there, done that, and it was not helpful.
Is there a college or university nearby with a piano performance program as part of the Music Department? If so, many piano professors also teach privately on the side. What you're looking for is a teacher with at minimum of a BM degree in piano pedagogy or performance. An MM or DMA degree is preferred. The teacher should also be an active member of a national or regional piano teachers' professional association. Keep looking. There has to be someone you haven't run into yet who can be truly helpful.
3. Things to learn. Once you find a teacher, you need to study hand positions, use of arm weight in attaining a singing tone, balancing the hands, voicing chords for melody and strategic harmonies, handling melody and accompaniment within the same hand, differentiating foreground from background in music, legato phrasing as well as staccato, portato and nonlegato touches, score analysis, determining sensible fingerings, voice leading, pedaling techniques, dynamics, accents, polyrhythms, expression, nuances, rubato, listening to yourself and hearing yourself, and much, much more. Some of this involves fundamentals and some of it involves fine points in the performing art. In other words, you need to achieve musicality through a keen sense of musicianship, and, one day, even artistry. For the serious student, there is nothing casual about playing the piano. It is a very lofty calling involving a profound sense of responsibility to serving each composer well when performing his works.
4. Repertoire. Once you find a teacher, you'll get much guidance on that. Basically, you want to be a well-rounded pianist. That means studying the various musical periods and styles--Baroque, Viennese Classical, Romantic, Late Romantic, Impressionistic, and Contemporary repertoire. Each period builds on the previous one and prepares you for the next. Generally, you should be practicing and playing pieces at your level of proficiency. To make continual progress, you'll want to occasionally select pieces at one level above your comfort zone. That will "stretch" your abilities and enable you to eventually move into that next level where it becomes your new comfort zone. Again, it's always preferable to play an easier piece very well than to make a mess of a much harder piece.
5. Do you own a metronome? If not, get one. You can use it in selecting proper tempi, figuring out a difficult rhythm, seeing how figuration actually fits into a complex measure, etc. You can also use it occasionally throughout a whole piece (not to make a habit of doing that, as you don't want to sound robotic in your playing) to find out if you stumble in some places--meaning you don't know those spots well enough to play the piece consistently as a whole at chosen tempo. Hand alone practice can be valuable in those instances. The metronome helps to discover and isolate problems in not allowing you to slow down for them. You can also use the metronome to do speed drills. To increase the speed of a piece, you can very gradually keep increasing the metronome setting to fool the brain into playing faster. It's a very useful and indispensable tool.
I guess I'll stop here. I don't know if any of this is helpful to you or not. Anyway, keep practicing. And find yourself a really good teacher!