I generally have bad control when i don't look at the plate, or have a and front leg/glove side. Make sure you tuck your glove side in, and have a firm front leg on FFS. A common thing that causes a loss in control is over rotating, by bringing your knee too far back (your back leg is probably a good limit)
Another helpful thing can be the "aim small miss small" philosophy. You're more likely to have a closer miss when you aim at a small target than a bigger one. Another helpful thing is envision yourself throwing strikes. A study was done with someone throwing darts where they had him try once, and then for a month told him to envision himself hitting the board with darts for 5 mins a day. A month later, they tested him again, and he had a 32% (I think that's the right number) increase in accuracy.
About your mechanics.. I've been in the same spot as you. I watched pro players pitching many many many times and it appears I have subconsciously changed my mechanics to theirs, as there has been a drastic change.. Without me ever noticing. This is also a phycological effect.