Zoloft/meds, motivation and concentration gone!

I have been on Zoloft for about 12 years and have recently been questioning wether or not It's still working.

I tried to go off for about two months but things got a little too tough and started back on them, this was about 6 months ago.  Since then my attitude has been awful.  I'm not like I used to be at all.  I'm tired and like to stay in bed all the time.  My concentration and motivation are gone.  I was a really outgoing motivated person who is now the opposite.  I was thinking of switching my medication but before I go to a Dr. for one opinion I thought I would get all of yours...

Thank you for you help.

I never thought I would be on meds but a long time ago someone close to me told me I should look into an AD because of my temperment.  I would get angry quick without going through 'steps'.  I would go from talking 'regular' to being explosive.  That's the original reason for the meds.  After my Zoloft took affect I found my 'range of emotion' is smaller and I'm able to let the 'little things' go more.

However now I'm just not myself and havn't been for about a year.  I used to be such a go getter.  I was also very comfortable socially.  Now I like to stay in bed even on a sunny day.  Going out for a get together somewhere seems like more trouble and anxiety than it's worth.  Projects that I initiate are now just laying around.  I'll make a list of things I need to do tomorrow then might only get one thing done or possibly none.  I just keep pushing things back until I notice that I've wasted months thinking about this or that and not doing anything about it.  Feel totally useless.  My concentration and motivation is nearly non-existant.  Socially I feel like I'm going backwards.