You gotta decide what you want to do/be my man.
Do you want to be lean? shredded? big and chunkier?
First decide what you want from your physique. Then you can plan on how to achieve it. There are tons of different ways. You are young, so you have plenty of time.
But I can tell that you don't want to be chubby. I don't blame you. You're almost 16 and are chasing girls. For the most part, girls really like lean.
My advice to you is to always always always eat clean. There is no reason for an endo to throw clean diet out the window. If you want to be lean and in shape for the rest of your life, you have to learn from an early age all about proper nutrition. Keep that. Eat Clean, but enjoy yourself.
I am an endo, and I can tell you are probably like me. It is a life choice to stay a lean endo. I will consistantly eat clean enough to keep under 10% bodyfat. It's not worth it to me to do anything otherwise. If you start now, you can learn how to get there and keep yourself there.
When I am maintaining, I eat extremely clean during the week. I enjoy myself during the weekends. I don't go crazy, but I let loose a little bit. This allows me to keep under 10%. When I want to shred down further, I diet hardcore... I'm still trying to figure that one out.
To sum up my point. Pick your path and stick with it, figure out how to get there and stay there. Eat Clean all the time. Even when bulking. Eating clean will keep you lean!
As far as your bloating problem: Drop the lactose. Cut down on the bread. No need for 4-5 pieces of toast at once during normal linear diet. If you are going to eat bread, go flourless ie Ezekiel Bread. Very healthy, very tasty, very low GI.
To keep your water balance in check: keep sodium in check. Don't irradicate it from your diet... But be cogniscent of it. Keep it relatively low.
Drink tons of water. 1 gallon minimum. Get 1.5-2 if you can.
Water retention also has to do with mineral/electrolyte balance. Potassium, B6, magnesium can be extremely helpful to supplement. You can your mineral balance from a good multi vitamin like dx-7 or animal paks. They are worth it.
If you gorge on the carbs, you will gain lots of water throughout the day.