[Massive]

I'm definitely differently-abled, and have been now for quite a few years.
I have rheumatoid arthritis and, since I tore the ligaments in my lower left back, I now have an on and off back injury to deal with, it can go from my literally turning my head.
Part of me resents when I get looks from older people now, because I sit at the front on public transport, here if you're disabled or elderly they ask that the first few rows of seats are given up to the disabled or elderly, and since the disability act was passed here a few years back, a disabled person has more right to be on a bus than someone with a pushchair and child.
I appreciate when friends ask if I'm able to do the same things as they do, although I keep reminding them that I've had RA now since I was 18, so I know my limits, I know what I can and can't do, and do my own risk assessment ahead of time. At the same time it does feel like some of them are trying to hand me this mythical 'pass' like a get out of jail free card in monopoly, to just say, "It's okay, we'll just walk slower/talk to hym like hy's slow because hy's not the same as us." kind of attitude.
The majority of my friends know beyond a doubt if they treat me that way they'll find out pretty damn sharply not to do it again, ever. However, I also have a certain group of friends, who I now rarely make the effort to see, who tell me I can't call myself disabled, because I don't look it, you can't see my RA, I'm lucky enough that it hasn't progressed to the point where my knuckles and fingers are twisted with it, you can't see my back injury, apart from when I can barely walk, and then I sometimes get "Oh, you're just too fat, you need to lose weight." yeah, that'd help, but what helps more is not having ignorant feckers say things like that to me when I'm already having a day bad enough that I can't just use my cane to walk, I'm using crutches.
I often want to say to these people, okay, if you think living a life like this is so easy, spend a day in my shoes, see what it's like to walk around feeling like there's a mix of ground glass and acid poured into every joint, try walking with someone jabbing you in the back with a knife at every step, try pulling your head out your arse and realise that just because I'm not the same as you doesn't mean I can't understand english, I'm not stupid, it's just my body can't keep up with the rest of me, and this is how I'm going to be for the rest of my life.
I do have a badge for parking, which stays with me so I can use it in whichever car I'm in, I do sit in the seats at the front of the bus, I do have to sit, making sure either my crutches or cane are visible so I don't get elderly people glaring at me accusingly.
I do have a life, I just have to live it a little bit slower and more carefully than those who have nothing wrong with them.
I am a human being, I deserve the same respect as anyone else so why is it so damn hard to receive this?

Also wanted to add, for anyone who hadn't noticed 'here' for me is the UK...