I work full time and have to pump at work too, so I know what you're going through! My baby is 10 months now and there have definitely been times when my milk supply was decreasing. So far (fingers crossed!) I have always been able to bring it back up by doing a few simple things:
1. I start taking Fenugreek, which you said you already tried. Make sure you're taking the right amount.
2. I start drinking "Mother's Milk" organic herbal tea, several cups a day. It's made by Traditional Medicinals and I find it at my local Whole Foods.
3. I make sure that I'm doubling my water intake b/c you won't produce if you're dehydrated.
4. I make sure that I'm getting "enough" sleep, relatively speaking!
5. I pump a few extra times a day, after the evening feeding, before I leave for work, etc.
6. I try harder to make my at-work pumping sessions more peaceful by turning off my phone while I pump, turn off the lights, look at a picture of my baby, put on some relaxing music, close my eyes and imagine that I'm at home playing with him.
7. Make sure you're staying away from caffeine and eating lots of fresh fruits and veggies.
It's been working for me so far. Within a few days my production goes back up! Keep up the pumping. It's a total pain to pump at work, I know, but it's 100% worth it. You are doing such a wonderful thing for your baby. Good luck. :)