Oh I remember the days of expressing into a syringe, the first time I filled it I cried so many happy tears. You will get there to hun. Make sure you are eating lots of healthy snacks, keep your water up. If the boys are strong enough do lots of kangaroo care. Also if one is coming off the drip ask about finger feeding. We used that when ds wasn't quite strong enough to suck the whole feed. Let me know if you want me to explain it better.
Next time the nurse is rude ask her flat out what she would have you do different, either she will make suggestions or look embarrassed she got caught out. Sending lots of strength and weight gaining vibes to your little men