I am depressed and stressed. can anyone help me this is a little confusing so you have to read the whole thing?

i am a 15 year old in 9th grade. i have been feeling depressed and stressed ever since 7th grade. my brother is basically my best friend and when he was in 9th grade (i was in 6th grade) he was admitted for crohns disease. he felt alot of pain in the stomach area, sometimes so unbearable that he wouldnt talk to anyone. he had to drop out of school because of this disease. seeing him like that made me feel horrible. He used to laugh with me all the time and do everything with me. when time went on it got a little better but he was weak from staying in bed too much he was already skinny and hardly ate anything unless it was made for him so it was hard to do stuff. playing soccer was the one thing that my brother (and i) love so much we like playing other sports and are quite athletic but to see him not be able to play from being to weak. sometimes he just didnt even try. it was horrible. then coming up to the present its a little better my brother is playing more soccer but i feel like he is addicted to electronics. when we first got an xbox 360(2 years ago) thats all he would do somedays now he has a laptop and he spends about 10 on average everyday on it. so that also gets in the way of us doing stuff together...now im not saying he should just try to be with me all the time because he can get annoying at times (when hes feeling good) and he should have his own life he is 18. my mother now is a big stress factor, she will point out things i am doing wrong like when she asks me to do a chore and im not doing something how she wants maybe using a different soap to clean the bathrooms or something she will yell at me and have a spaz attack... she has been doing this my whole life and about a year ago i have been geting really ticked off about it because its evrylittle thing. my dad suffers from depression (not a big thing) and sometimes i think i can talk to him but hes the one person i really look up to because hes really smart, funny, athletic, brave, honest,etc. all the good things. and i guess i feel like if i relate to him on something that would make him seem weaker i wouldnt see him the same way. now my oldest brother and oldest sister (i am the youngest of 5 children, it goes christy, david, peter, katie, and me) bothh are depressed. my oldest sister left my house when she was 17 she found a job being a waitress and got an apartment and moved away, mostly because of my mother being annoying, and whats sad is that she was another person that was like my best friend, not as much as peter but i could talk to her about stuff more than my parents and katie and david...now david is like emo kinda he ascts all dark and depressed like his most used response is "i dont care" or"it doesnt matter" example: mom says"david have you eaten," david says "it doesnt matter". another emo thing he does is if katie is talking sometimes she will say stupid things, alot of people do from time to time but katie says it more, a thing david will do is have a disgusted look on his face sneer and shake his head. ive made jokes about it because it is funny but i wish he were different. I no ive written alot and there are spelling mistakes and the whole question is probably not right like ill go to peter then my dad then back to peter. also i felt better writing down everything and felt more relaxed puting everything out. this is the first time ive ever put this whole thing outside my head