I just wrote a mammoth post and when I went to submit it lost it

Maybe its for the best as it was possibly a little incoherent!
The main just of it was that i feel like I've spent my whole life suffering from anxiety/depression in one form or another and that i have this problem with getting stressed out so easily with life that I'm not really able to handle very much going on at once. This is a real problem for me at the moment as I'm finding that I can't really cope with anything at work as even the smallest task is paralysing me and I'm feeling like I'm such a failure in relation to my other colleagues who are on the same level as me.
I'm very distressed at the moment because i feel like my brain doesn't work in the same way as other people's, it isn't interested in learning anything new and its not able to take in and process information very easily which means I'm very slow at work and can't think on my feet or come up with good creative ideas. I take so much longer than other people to complete tasks and I'm really worried that I'm going to eventually lose my job because of it and then I wouldn't be able to get a new job because I can't do anything on my own initiative.
I feel like I'm simply not able to think intelligently about things or to think about and query things at all for that matter, I'm meant to be going to a conference for work next week and I'm completely dreading it because I know i won't be able to focus and then I'll really struggle to report back afterwards.
I've always been scared of hard work and challenges and I've got myself into a complete hole at the moment which I just can't climb out of. It really feels like the darkness is closing in and closing down my brain and i just don't know how to stop it.
I don't really do anything of worth and I feel as if that's never going to change and therefore there's really no point in me being here at all.
I'm not really sure what I'd like to get from posting on here, probably just reassurance that I'm not alone in how I feel and some advice on medication as well as i had been on citalopram for a number of years but have not been taking it for around 8 months now and am thinking that i would like to find something else that may work better for me.
I don't quite feel this post says everything that I'm feeling right now its certainly much shorter than my last one but I'll leave it as it is and hope to hear from some of you soon.