This is exactly what I went through with DS1 & 2 at the same ages. Given you had such a over supply I think it's improbable that you are losing supply unless you aren't eating enough yourself. I just tried to ride it out and got ds1 weighed weekly during that period for peace of mind. He was making massive gains so I knew even though I felt drained, milk was there. It should settle down in a week or so!!! Good luck!!!!