Hello~
I am by far no expert...but after BF'ing for 7 months, I think I've learned a couple things! ha ha
First, I have noticed that if I'm stressed, that really decreases my supply. I once worked for a month to get my supply back and tried everything...but once I finally relaxed, it came back. I'm sure trying to relax with a new baby & toddler is impossible...but really...try to just sit down as much as you can to give your body a break during the day.
Of course, keep trying to get him to latch on because his sucking is the strongest cue to your brain for letdown and to make more milk. I know it's REALLY frustrating, but even if you just try for a few minutes before each bottle feeding that could help. I've read that your brain memorizes your babies sucking pattern, so doing extra pumpings to increase your milk supply might not send the best message to your brain to make more. Pumping extra does work for some, but it didn't for me. If you think it is working for you though...you could try getting a insert for your pump flange (the part that is in contact w/ your nipple) for extra stimulation.
http://www.breastfeedingworld.com might sell your pump's brand.
Also, make sure you're eating enough carbs, fat, & protien and drinking more, more, more water! My friend said she started drinking a gallon of water a day, eating better, stopped stressing, and her milk came back.
As far as a slow letdown...the only thing that helped me is before a feeding to take 5-10 minutes to relax and clear my mind, yet thinking about feeding the baby. Then in a quiet room, after he latches on, close your eyes and breath deeply and just focus focus focus on a letdown. Keep your muscles relaxed and not tense. I KNOW it's hard not to tense up when the baby's coming un-latched...but even if he suckes for a little bit, stops, then a little more, stops, then a little more...that could trigger a letdown.
And....my lactation consultant suggested not going too long between feedings so that he's not so mad when it's finally time to eat. Try a tad sooner to see if he's more calm.
Hopefully that helps! If you BF your 1st for a year you probably knew most of that, but if not...I hope it works.
Also,