Hi OJNR and welcome - I too sympathise with how you are feeling. I am fortunate to be in a relationship and with a man I adore - but when I was at my lowest last year, this wasn't the case. I was still in the same relationship, but I also had a really good friend (who i call 'Peter' because, I don't know... feels like it protects his identity a bit, although it doesnt actually make any difference....) annnnnyway, Peter was actually my OH's friend to begin with, but me and him had more in common and we just clicked. Before long we were doing things together when my OH was at work - not secretly, but Peter can get days off at the drop of a hat (he's a temp) wheras my OH is in much more of a steady job, where he is needed! We got very close - best friends. We would stay up chatting and drinking when my OH went to bed, we'd email or chat on msn throughout the day when we were both at work, I ended up working near him (not necisarily on purpose, but it was an added advantage at the time) so we would go into work together, have lunch together and then when I got ill, he was a rock. Because of his ability to get time off, he would come to appointments with me when my OH couldn't get the time off... I confided in him, he knew every single thing about my illness. (My OH did too... ) But then... Obviously, this didn't go unoticed by my OH - when Peter started buying me things, or ringing my pshycologist without my consent, it was really the final straw. My OH told Peter to back off - which he did, but within a few weeks, he was back to normal. We had a big bust up eatlier in the year when I discovered Peter had taken a photo of me asleep... my OH hit the roof! And I wasnt too pleased either.... and we havent seen each other since

that was around April... I still speak to him pretty much every day, although his name is like a swear word to my OH! But I miss him so much. Everything is tainted because I now wonder what exactly he was getting out of our 'friendship' but it doesn't alter the fact that we had so many good times together and I still care about him, a lot! i go through phases of being angry, upset, guily, remorseful.... everyone logical, even the logical side of my own mind tells me to move on! He ended up being a destructive influence and probably not helping my illness one bit as I was the one that ended up feeling like I was constantly caught between my fiance and my best friend! But... I can't. I want our friendship back so badly, but I know it'll never be the same...
My relationship with my OH though has never been better - he has been
so supportive and there were so many times when I acted like a complete twat last year and he would have had every reason to leave me. But he didn't. In a funny way, all of this has made us stronger! So I know... If me and Peter were to start being friends that actually saw each other again, it would really hurt him

So - I know how it feels to know that just moving on and 'forgetting' someone is so clearly the wisest thing to do - but also the one thing thats impossible.
Also the feeling that you are wasting your life - get that 110% I get so frustrated when I think that for a over a year I have done nothing more that try and make the depression go away - its an achievement if I manage to do housework in the day!! I'm 26 for christs sake, I should be out seeing the world, doing so much before I have children and get old... but it feels like everything is passing me by and I am poweless to stop it...
As Depina says - try and keep on with the Citalopram. the first few weeks are the worst for any side effect but over the next few weeks, you should start to feel a little better &*(
Take care x