Self esteem and chatroom addiction

[William]

I'm a 21 year old male bisexual.
I have had self esteem issues since I was about 14 years old. I think it all started one day when it emerged that this very pretty girl fancied my friend at school.
At the time I'd been overweight for a while and forgotten that brilliant feeling of somebody liking you when you're that age and I suppose I realised I wanted some of what my friend was getting.
Since then, I've not been able to shake off this obsession with how I look, particularly my weight. All my life, various people have told me I'm a good looking lad, but I've had numerous episodes where I was chubby and took a lot of stick for it at school.
I've never been a dieter, because I don't believe in them, and I've certainly never had an eating disorder, but I started the Paul McKenna I Can Make You Thin
regime almost two years ago, lost four stone in total and have managed to keep it off.
For a period after that it felt like so many people fancied me.
Since I was around 16, I've spent way too much time talking to people over MSN/Skype that I meet on chat sites. Before I lost the four stone, I'd had a lot of rejection
on there, then suddenly it felt like whoever I met would be really interested in me.
But that's since become less and less the case. I haven't put the weight back on. I literally don't know what looks different about me, but when I've been on these sites recently
it feels like I have as poor a chance of finding someone that likes me as ever.
It's so hard to take that I was finally feeling great about myself, and now I just feel as low on confidence as I ever did.
Because I've never been one to get out much, I think I've relied on these sites to give me the self confidence I need, and over the years it has grown into
a bigger and bigger addiction. There's just no inbetween in terms of how I feel about myself. I meet someone that likes me, and I feel on top of the world. I meet one person
that's not interested, and I feel angry and depressed and self loathing.
I hate myself for feeling this way when there are so many people with plainly bigger worries than their looks, but I would give anything to not care as much about it as I do.

I've been able to put the feelings to the back of my mind in the past but they've recently been dominating me and being a lad, I find it harder to confide in people about it.

Thanks for reading and for any words of advice or comfort you might have.