pump or give up

My daughter is about three weeks old and I'm feeding her formula cause she won't latch. I pumped in the hospital right after her birth and was surprised at my milk supply (it was more than I'd ever had before). I got home and my supply started to dwindle. I have a 9 year old and am a single mom. My dad has been living with me and helps out a lot. I still was very stressed and overwhelmed and hormonal. I think that's why my supply dwindled. Anyway, I've been pumping every two hours and drinking lots of water and taking fenugreek. It seems like my supply is dwindling even more! My question is how many days does it take to see an increase and is this worth it? My daughter gets not even 1/2 an ounce of breast milk.