Reason for losing weight?

Yeah i feel really at home here and good to talk to people with the same interest as me!!

I've always been underweight. Im a lazy ass person, in fact so lazy that I avoided eating if its not in my comfort zone. When I finished my college and started my first job, I was 10 kg underweight (17.5 BMI).
I moved back to my parents' place after a serious illness and now I've gained enough weight to have a full flab.
Im so used to looking at a malnourished belly that looking at my fat makes it seem alien. So...

My reasons were manifold. For as long as I can remember, I've been overweight. I'm 26 now, and until last year, I'd been a size 18 since the age of 18.

I was out of a job at the beginning of 2014 and ended up working back at somewhere I'd worked before and vowed never to go back to. The pay was minimum wage and after paying bills and debt payments, I could barely afford to feed myself, so I subsisted on a lot of frozen and processed crap. I put weight on and my size 18s started feeling tight. I lost all confidence, and though I knew I needed to do something, I couldn't find the motivation.

Then I met my now-boyfriend. He told me about how he'd woken up one day, looked in the mirror and hated what he saw, so he decided to do something about it. He changed his diet completely, started working out, and lost 4st. I thought, "Why can't I do the same?" After we figured out that we were made for each other, and it turned out that he has kids from a previous relationship, I also realised that one day I'll be a part of their lives and so it's my job to be in a good place health wise so that I can be a good role model and not give them any reasons to worry.

I've now lost nearly 3st, dropped to a size 14/16 top and size 14 bottom, with just over another 2st to go. I don't remember ever being this clothes size, and on the days where I've got my head on straight, it feels really good. Onwards and downwards.

I have always been fat ..or should I say chubby from when I was young having been quite an ill child so not able to exercise at all. Then in my young teens I had rheumatic fever again and was in hospital for about six months just at the time that chocolate came off ration. I remember frantically writing to all my family to ask them to bring me some and ended up with piles of it which I then munched my way merrily through thus putting on loads more weight. Since then I have been on numerous diets .. lost lots of weight and then put it back on again time after time.
Now at the age of 81 I really need to get to grips with this as it is now affecting my mobility and whilst I haven't been much of a nan in the past I really would like to see my grandchildren and great grandchildren much more if I can.