Congrats on sticking with it! First of all, 4 month olds do still need to eat at night, and are usually ravenous first thing in the morning. THey have started noticing the world around them during the day and often take in less calories because of this. They make up for it at night! It's totally normal for him to be hungry even after feeding all night!
As for pumping, I hear you! I worked with my first, and pumping was a nightmare for me. I had ample supply but didn't respond well to the pump. That said, my son had nothing but breastmilk for the first 7 months of his life, and barely had solids until a year, so breastmilk sustained him. I managed to pump enough. He was 22 lbs at 6 months old and never had a drop of formula in his life! Here are some of the things I would suggest:
Make sure you are drinking enough water. Keep completely hydrated.
Eat oatmeal for breakfast every morning.
Mother's milk tea (Kroger even sells it in their natural food section) can help tremendously.
There are herbs (fenugreek and blessed thistle) that you can take, but I wouldn't do that as a first resort.
What about your pump? Are you using a Medela PIS (most popular one, it seems)? The flange/horn thing (the part that actually touches your breast) is often too small for most women. They sell other sizes as well. I had to get the size large ones, and it really helped me to pump more. The regular size that came with the pump restricted milk ducts and I wasn't getting enough with them. You can buy the bigger ones online.
I actually yielded better results with my manual Avent Isis than the Medela PIS! It's really a great pump.
And most of all, relax! Take the moment when you're pumping to think about your wonderful baby, look at pics of him, bring the pjs he wore the night before and smell them, drink your water, and revel in the moment that you are providing sustenance for your little one. Relaxing will help a lot.
And very importantly: nurse as much as he wants (on demand) when you're together to keep supply up. Don't worry about bottles on the weekends (or whenever you don't work). Just concentrate on nursing. It's even sometimes recommended to take a "nursing vacation" where you don't work one day and just nurse on demand. It will help up your supply to keep you on track.
Good luck! it's not easy pumping, and I congratulate you! There is no shame in giving formula, but I tell you - it CAN be done to pump for your child and never give a drop of formula.