Hi kizzie definitely exercise has helped me.
Because I am reducing all my medication in order to TTC, I needed something to kind of "boost" me, if you know what I mean.
I am now down to an eighth of my mirtazapine original dose. Am so very nearly ready to stop which is amazing. When I was in hospital with PND I was on 11 different drugs at one point 
It has been such a battle to get off them all, but one by one, I have done it.
I did have a period of feeling anxious and low when I started reducing the mirtazapine. I was scared they would make me go back on it, and my chances of another baby would evaporate.
So I had to do something.
Exercise for me has been a bit of a life saver actually. I see it as a kind of "natural anti-depressant". It's hard whilst your doing it (getting hot, puffed, muscles aching etc.) but afterwards when you've showered, got changed it just feels so good! You kind of "glow". And the added bonus for me is that if you do it in the afternoon / early evening, the sleep is sooo much better too.
I basically try and do 30 minutes every other day - has to be enough to get me out of breath and red in the face for it to work for me.
I do believe you will get those lovely content moments back kizzie. It's great you are coping at work, in spite of everything. I'm sure you will get there.
xx