Hi there
My hair is currently trashed too, I'm going through the process of impatiently waiting for it to be better.
My damage is due to colour, I heavily highlight and blonde colour my natural brunette hair. Despite that, I usually have gorgeous condition, lower than bra strap long, thick smooth hair. Hairdressers have asked me how on earth I do it, it's good care but that's not the info you need right now.
I have however twice in fifteen years had a complete catastrophe with damage and ended up with massively broken damaged birds nest crazy, once because I was unwell and let my hair care rules slip for a while, most recently because I moved countries and three hairdressers messed up the colour, meaning it needed redone, which absolutely destroyed it. Broken, frizzy, have already had to chop a good twelve inches off it and it's still an embarrasing mess.
However I can tell you this. Yes it can get better and you plus a good hairdresser (you are important too, there's lots you can do!) can heal this and have is grow back and stay healthy.
- Heat, straighteners, bad. Bad bad bad. Try to absolutely limit these. I never use heat because I colour mine and hair can only take so much. Straighteners are notoriously bad even for hair that isn't coloured. You said your hair was frizzy but not curly. Have you seen a stylist and asked if they can teach you how to style your hair into a natural curl of wavy style? The right products like mouse, not brushing waves or curls and using hair dryer properly, or not at all, can turn frizz crazy into gorgeous curls or waves. I would ask about learning to do this, then let your hair be natural and give it a rest for a while.
- If you wear your hair up, only use a loose clip or a scrunch (they are back in fashion, yay!). A band for a pony tail will literally damage and break your hair, particularly if it's already fragile. I wore mine in a wound up top knot day and night the first time I trashed my hair and after three months it was so broken and trashed. It was gorgeous again within a year which surprised me given how messy it was, but now hair is only ever loosely up for the gym and I leave all the front parts free as they are more fragile.
- Hair whilst you sleep, first get a silk pillow case, they're not expensive and you can get them on amazon, they massively help with split ends, frizz and damage.
- Also think about how you wear your hair whilst you sleep, for me that means never putting in a loose top knot. For your hair type, ask a hairdresser how to avoid damage and keep it as smooth as possible.
- Chop off as much as you can bear now. Trust me, I feel your pain. Split ends travel up causing more breakage damage and frizz, so they have to go, even on layers, broken and mismatched places. If you don't, it just won't grow out healthy, it continues to feel like you're getting nowhere. So get rid of all split ends and as much damage as you can bear.
- Biotin! Now this is a good one and a new discovery for me after the most recent catastrophe. Biotin capsules are a supplement you can take that helps hair (and nails) grow healthy, stronger and more quickly in some cases. I've been taking it for about three months and I really notice a difference. It doesn't suddenly grow two inches in a month as I half hope, but I can see growth by my natural colour coming in and it's definitely a bit faster. Plus all my new hair since I started this is shiny silky perfect. It's a few inches of that then bird's nest, come on hair! I noticed by my nail varnish that my nails are growing more quickly too plus are stronger. You can buy it on amazon, it's not expensive.
- Coconut oil treatment. A fad that it turns out is real. I have always used deep conditioners and good products for my hair type so I didn't expect to see much difference, but wow, silky smooth difference! I don't sleep with it overnight as I tried it once and it didn't seem any different to just half an hour, but some people find overnight occasionally is helpful. You out the oil through your hair when it's dry, let it sit (with a warm towel is apparently popular, I just go for drip all over me), then wash out. Wow. Organ oil every time my hair is washed, before putting a brush or dryer near it, unbelievable difference, one of the things that kept my hair in fabulous condition and something I let slip just around the time it was destroyed the second time.
8.I don't have these, but what about the brazilian blow dry thingies? Meghan Markle style. I think they smooth out wavy, frizzy and even natural hair like Chic Ms Markle's into a straighter style and it lasts quite a while without doing damage. If the curls don't work out for you, that might help with smoother, avoiding straighteners and improving strength of hair. Also day to day, get the right type of shampoo and conditioner, plus deep conditioning treatments, for your hair. I stopped choosing the one I liked the smell of the most and changed to for my hair colour, I see a big difference if I change even for a couple of weeks.
My hairdresser when I lived near you was freaking incredible (town not city, twenty mins on the main intercity train, probably you can guess which town, send me a message if you'd like her name, fraction of price), she was the reason I was able to grow back completely broken destroyed coloured hair into gorgeous long silky healthy hair, even with the lightest possible highlights and colour all the way through it. I'm not sure how she is with your texture of hair but you could give her a call and describe what you're dealing with and get a feel for her based on her advice.
As I'm telling myself right now and I am believing albeit impatiently because I have experienced it before, yes you can absolutely massively improve your hair. I had a wrecked and chopped to one year gorgeous long smooth even and healthy, it's just constant care in some ways and constant leave it alone in others!
Good luck, again, I feel your pain. My instagram is going to be throw backs for at least the next year, that's how bad mine is:)