I need help with my husbands selfishness?

I have been with my husband for 5 yrs married 1..we have 3 kids ages 1,2 and 3 yrs..i am a stay at home mother and wife! My family means everything to me I bust my butt taking care of everyone..I don't ask for much. My husband gets into these "hobbies" something hes always wanted..turns around and its not good enough..then sells whatever it is to get another "hobbie" cuz its what he wants. Here in the last 6 months he has spent thousands of dollars on guitar stuff, he wants to be this big country star! granted he is a great guitarist..but come on..I had a trailer that was mine from another marriage i sold it thinking i was gonna get what i wanted...he said i could that it was mine..He then turns around and asked me for 700 dollars..I was floored! mind you all the stuff he sells, he sells to get what he wants..i never see a dime outta it...it makes me feel terrible! I ended up giving him money out of "MY" money..at first i told him no way..he was mad acted like a 3yr old! He recently sold some stuff to get a 1500.00 dollar guitar..Does he not see that i feel like a big bunch of nothing? We fight like crazy he plays guitar all day when he is off with music so its always loud in the house..or he is sitting in front of the computer learning about guitar..he never helps me around the house i ask..but if i want it done i have to do it..I feel so trapped, used, hurt, worthless. I don't know what to do anymore...now hes got this band thats about a 2hr drive from where we live..when i say lets go do something,,he says thats gonna be a 200 dollar bill..or something! why is it ok for him to have all the damn pleasure in life while i stay home? the other day he told me i was a free loader..that tore me up! Im sick all the time..Help