I’m 21 years old. I’m 5′9/175cm and 72kg/160.9lbs, which makes my BMI- 23.8.
I know this is a healthy weight, but I don’t feel healthy. I have had comments made about my weight by my grandfather on both side, my grandmother, my mother, and others. So I need to lose weight. I’ve been this weight/height since I was about 18, although two years ago I lost about 10kgs/22lb, but it’s creeped back up to where I was before.

I have Coeliac’s disease (so no gluten). My diet consist of the following-
BREAKFAST
Gluten free cornflakes or rice bubbles with tinned fruit (in juice) or a banana with skim milk and 2 tablespoons of sugar.
or
Gluten free seed toast with either peanut butter and banana or avocado and tomato.
LUNCH
Ham or tuna salad, lettuce, tomato, cucumber, avocado, light mayo, tablespoon of pesto.
or
8 pieces of small salmon sushi
or
scrambled eggs (no oil) on gluten free seed toast.
or
one toasted cheese sandwich with cheese, ham, tomato.
DINNER
Chicken stirfry with veges and rice.
or
eggs and toast and a sausage or a hashbrown.
or
gluten free pasta with low fat mince, light pasta sauce, veges and a bit of cheese.
and then
Fresh fruit or tinned fruit or a biscuit. A slice of toast if I’m still hungry or a hot chocolate.

I may have a few squares of chocolate or a lolly or two. I drink at least 8 glasses of water every day, most days I have more. I may have a drink of orange juice or a glass of diet fizzy drink/soda.
As for exercise, I have arthritis and Chronic Fatigue Syndrome, so I do my very best to exercise. I get 30-50minutes of brisk walking 3-4 a week. This is all I can manage at the moment, but I’m trying to increase it (but I really need a rest day in between). I also have no access to a swimming pool.

So what am I doing wrong? Thanks.
Wow 5 spam answers.
I don’t use any butter, if anything I use ultra light margarine. The only time I use cheese is on my pasta or in a toasted cheese sandwich which is once or twice a week. It takes me 6 months to go through a block of cheese.
Skittles- I’ve had B12 deficiency for a few years, but since going gluten free it’s pushed it up over the line. There’s olive oil in the pesto that I have.