sTTN -supply issues?

[Droflove]

Hi, my ds is 12wo and has been before till about 2 weeks ago when I introduced formula for his dream feed (dh gives at 10-11pm). It's going really well and I express as much as possible from 9-10pm so to not damage my supply. I use the expressed bottle the next day to top up my last bf of the day at about 7pm. He has started sleeping till 4 or 5am recently and at first I was v. Uncomfortable with engorgement but it seems to have settled down at night to match his pattern which is fine but now I am paranoid that it is affecting my daytime supply. I only got 3.5oz expressing last night at 10 when my previous feed had been at 6pm! Surely I should have had v. Full breasts by this point? I really want to continue bf during the day so any advice would be welcome.

'Been ebf'ed till about 2 weeks ago....'

I think at that age, you need to express once in the middle of the night, if you aren't feeding, like at 2 or 3am... that helps keep the supply up.

any reason you are using formula? do you express whenever the baby gets a bottle? other wise your body may think that milk is no longer necessary

I read that formula is twice as slow to digest which is why ff babies tend to sleep longer between feeds. I was trying to gain that advantage as well as have one part of the day that wasn't reliant on me.