Hair dying- scared my hairs going to actually break!?

okay, since i was about 14 (i'm not 17) i've been dying my hair i'd say every 5 months or so. I've only ever used 3 permanent dyes within these years, and the rest semis. I straighten my hair about once every three days, and wash it once every 5 or so, because my hair is very dry. Within this time I use talcum powder as a dry shampoo if it looks greasy to try and minimise washing. about three weeks ago my mate works at toni and guy and he dyed my hair a semi reddy colour, my natural hair colour is a flat medium brown, and i loved it, and i've onyl washed my hair twice since but now i'm offered to model again and recieve the same semi permanenet. Im starting to worry cause people are like woah your hairs gonna fall out, and it looks really dry, and taily like all flyaway split bits of hair, and its so thick and frizzy looking. I;d never have the guts to cut off my hair completely but i'm, scared i'm going to have to. my wquestion- does reddy semi's damage your hair? am i advised not to repeat this, or will it nourish my hair? ALSO, how can i minimise straightening if my hair is like a wolf when dry?xxxxxx