damage? Dryness? What does my hair need?

Does it feel mushy when wet or overly stretchy? take a single hair and stretch it, a healthy hair has some stretch but goes back to its original length, and unhealthy hair will either break or stretch too much like chewing gum.
It sounds like you may just be tangling it when you wash, are you scrubbing the shampoo in?
I brush to untangle, then add conditioner or oil to my ends before washing to help prevent washing tangles. Washing can cause a lot of mechanical damage to long hair
I would also consider a milder shampoo or diluting it with water or conditioner before use. CO washing would be even gentler and less likely to tangle

Thanks for your help once again Wicked Pixie! I'd heard some people say about the stretchy, chewing gum feel so I tried that and I think it is a little stretchier than it was but certainly not to any significant degree.
Thinking about it, it really could be just an issue of the shampoos I have at the moment as I'm out of work and unable to claim benefits where I live at the moment so I have been having to scrape by on the cheapest stuff, I'll try diluting them a bit I think. I did try co washing last year but I couldn't get into the swing of it, my scalp kept getting itchy (which it does if I don't wash my hair frequently anyway) and my hair was very limp all of the time.
Thinking about it another issue is that last time I had long hair I didn't colour it at all so this is probably the first time I have felt the texture of the back of my hair with colour on it at more than a couple of inches long in about 10 years! I think I'm just panicking as I finally have luscious collar-bone length locks and I don't want to damage it!

It does sounds like it could be harsh shampoo and mechanical damage. The hair cortex swells with water when it's wet and this itself is "wear and tear" on the hair, one reason why long hair doesn't suit daily washing.

My suggestions are similar. Coconut oil 10 minutes before washing, or condition-wash-condition.

Well I've managed to get down to only washing it every 3rd day now, but after that my scalp gets itchy, but I think that is helping the condition a bit. I have been using coconut oil too (I used to be allergic to it when I was younger but it seems like I grew out of it as it seems fine now) but I'll try the condition, shampoo, condition route too and see if that helps.
Thanks for the advice, I just wasn't really sure what the signs of serious damage look like and I didn't want to make things worse!

Edit: I think a good deal of it was down to the shampoo! I switched to an ultra cheapo own brand tea tree one and the matching conditioner and it seems much better, plus my hair isn't getting as greasy and my scalp isn't getting as itchy! Result! (weekly coconut oil treatments are helping too I think!)