hair growth

hey ladies! need some tips on hair growth. I used to have beautiful long hair. then I started washing it, blow drying it and straightening it every day. I started to get split ends and they would just break off. this was years ago (probably 6 years ago) however for about 3 years now, I've changed to only washing my hair once or twice a week, and using heat a maximum of once per week if I have to go out or something. my hair doesn't seem.to get any longer. it's just past my shoulders and has been stuck at this length forever! I've given it good trims, and it will grow back to this length and that's it. any tips on how to get it to grow longer?