It's so disheartening when this happens- but I agree if you have a food diary it might help? Sometimes with the best will in the world you're just overlooking something really simple which over the course of a week can make the difference between 1/2lb and 1lb, which is already a start
I thought that Fat Free Vanilla Onken yoghurt was free food for a few weeks, and ate A LOT of it- found out I was SO wrong! I also went through a brief stage of mistaking smoked mackerel for free food. Where I eat a lot of tinned mackerel, and just saw it in the shop one day and thought 'oh that'll make a nice change', however this only really changed my then regular losses into STS weeks (and even a small gain if I remember, when I find something new I tend to go overboard with it!!). My point is it can be a really small tweak that’s holding you back.
Otherwise, if you're exercising the same as the others, have the same amount to lose as the others and are eating the same as them, it might just be the way your body is reacting for now. If you had bigger losses when you started it might have been the initial 'shock to the system' losses that most people see when they first join, and do really well for the first couple of weeks, then for some people it settles down into a 2lbs per week pattern, and for others 1/2lb per week pattern. Even for people who are less fortunate in that way can do things to boost their losses.
I say 'for now', as for as long as you're eating well and are exercising (and even really if you're not exercising too much- I lost all my weight last year without moving a muscle, and ironically have joined the gym now and can't seem to budge the scales!!) it should catch up with the hard work you're putting in and start coming off faster. It can take the while for the body to realise ‘oh right, so THIS is the way we’re doing things now’ and start to play ball.
Other things to consider, just as additional food for thought: do you eat a lot of salt, as that can add to fluid retention, as can hormones obviously? Are you definitely getting ⅓ superfree over the entire course of the day (including snacks)? Also, if you're exercising a lot then the tired 'inches not pounds' cliché comes into play- it's boring to hear when you wait for the scales each week, but it really is true.
Have you measured yourself? That's a good incentive for times where losses can be slow, as even the smallest change in tape measure numbers is tangible and can be a good boost.
You could attempt a dreaded scan bran challenge, do the green tea challenge, drink hot water with lemon, try success express, up superspeed soups- there are lots of options for you to consider before resigning yourself to slower losses… some of them may be gimmicky rubbish but you may just find that magic ingredient that works for you and speeds it up.
Otherwise, no matter what combination of the above or else you're going through at the minute- if you're definitely doing it right and you stick with it, it's bound to catch up and come off at some point. Stay with it, even at 1/2lb per week you'll move it all in the end
(…sorry this is a bit more longwinded than I’d planned!!…)