Your problem is that you speak of being consistent yet regardless of the reason for changing around the program, be it boring or trying to find the best fit, that is the definition of inconsistency. Seasoned lifters know what works for them because they have usually spent YEARS changing programs, mainly spending a year or two milking what they can from each and reverting back to what garners the most growth.
Being 16 with 18 months under your belt isn't enough time to experiment, go with tried and true routines and after a year on it, see how you grew...that is consistency. Try stronglifts 5x5, if you top out but like it, go for madcow. If you have no intent to do a comp in the near future, go for 5/3/1 and insert whichever template meets your current goals, if you have the patience to run it, i've never heard of it doing poorly for any intermediate lifter.
But having mid range numbers and 18 months under your belt isn't enough time to merit changing from more than the original programming to a second program so don't get butt hurt when guys on here tell you to find a solid, proven program and stick with it, or tell you that your problem with growth comes from not sticking to any program because shy of intense peaking cycles, nothing will give you massive gains in a couple months unless you are a newb running starting strength.