For 10 years I was size 16-18 and "happy" with it. Then I gave losing weight a proper try. Not just a "oh I've had a bad day, I'll throw myself off the wagon" or "I'd lose weight, but I love my takeaways/chocolate/wine too much", but I proper stuck to it, trying all sorts of different things. I changed my attitude to food, and the way I ate. My main source of fatness (as it were) wasn't the take aways, or the chocolate, or the wine, it was the portions.
I'm now a size 10/12 and I LOVE it. I still enjoy take aways, chocolate and wine, I just don't pig out. I'll make a take away last 2 meals rather than one. I'll make 3 squares of cholocate last half an hour rather than inhale two whole bars.
So many little things I love now that I'm slimmer - I never catch my reflection in the mirror and get a negative feeling, I'm often complimented on my figure(and was massively hit-on on a night out a while back - I didn't know what to do!), I'm happy showing off my tattoos (that I love, but was always self conscious about being the "fat one with tattoos"). I've got loads more energy, can play with DS properly, when I have a rough day with both DCs, I don't collapse exhausted on to the sofa at 4pm. And thin sex really is better.
I'd say try it - really give it a go, set yourself a target, and see how it goes. Try whatever it takes to lose weight, whether it's cutting down on carbs, calorie counting, using Alli, loads of exercise or whatever, try them all and see what works for you.
Oh, and iirc, it's 90% of people who lose weight on Weight Watchers put it back on within 5 years, not those who lose it in a more natural, sustainable way.