Just began breastfeeding again...

At 5 days pp, we had a really rough patch and I ended up exclusively pumping. Well, we went to his one-month checkup today and my doctor got him to latch, and ever since, I've been able to as well. He's nursed three times so far until he's content and then falls asleep. But here's my problem(s): he seems to have a horrible time on the left side (which only ever pumped about 1 oz; the right always pumped 3-4 oz), pulling off every so often and shaking his head like crazy, batting his arms. On the right side, he's usually fine and eats for a long stretch. I don't know how to make it easier for him on the left. /: the other problem is that my boobs are like overflowing on him. During our last two nursing sessions, we both ended up soaked with milk lol. He ate until he was full, but there was so much excess that it leaked out of his mouth and spilled all over every time he pulled away. Has anyone else dealt with this? Is it because I've been pumping for 3+ weeks and my boobs are used to producing more than he eats? Will this stop happening after we get used to nursing again??