If you are a "plaque factory" as your unhelpful dentist so eloquently puts it then the following should sort that out:
Understand that plaque is formed as a by-product of the bacteria in your mouth consuming the carbohydrate that you eat. Sugar , honey, candy, chocolates, wheat, pasta, bread, cakes, cookies, cereals, sweetened yoghourts. desserts etc. Also from the carbohydrates that you drink - of course sodas (cocoa cola etc) but especially FRUIT JUICES, smoothies. Every single time you put anything like this in your mouth you will produce plaque.
Weakened teeth can also be caused by the acid which is produced when you eat carbohydrate. Every time you eat carbohydrate, your teeth get an acid bath. They can cope with maybe 3 times a day (when you have a meal) but start eating/drinking carbohydrates between meals and you are heading for problems.
You can ease the "plaque" and "weak" teeth problem in 2 ways - firstly, by reducing the FREQUENCY of eating/drinking carbs along with the amount. Secondly, reduce the bacteria level. You can do this with frequent brushing, mouth rinsing and by using XYLITOL. 6 grams of xylitol spread throughout the day either by chewing xylitol only gums or by putting the xylitol "sugar" in a bottle of water and drinking it throught the day. Xylitol works because the bacteria will ingest it but they can't digest it so you don't get the acid attack or the plaque. Your gums will also start to look healthier with the reduction in bacterial levels.
As a former dental hygienist I love xylitol - it's an easy thing to use.
As for your brushing technique, buy some disclosing tablets (or red food coloring). Brush your teeth as normal then disclose them. Note where the pink/red areas are and brush it away. Keep doing this and you'll begin to see that you probably miss in the same spots all the time and you can concentrate on NOT missing those areas.
Floss. Goes without saying.
If you are grinding your teeth at night, then go and see a dentist who can sort this out for you. It may mean a simple adjustment of the way your teeth come together or you may need a plastic night guard. This treatment may save you thousands in future dental bills.
One other thing.... since you say that you don't eat candies/sodas... does your mouth get dry overnight? This is often overlooked but can be causing your problems.
One more ..... do you have any kind of auto-immune disease like celiac disease? that's a whole other kettle of fish.