Sleep and milk supply

Natalie β€’ Angel baby, Jesse 26/02/2017 πŸ‘ΌπŸ» rainbow baby, Jaxen 07/07/2018 🌈 another rainbow girl, Alessia 05/02/2020 πŸŽ€

I'm currently combination feeding, I wish I could exclusively breastfeed but poor baby was dehydrated a few days after birth and lost 10% of his birth weight, so we had to introduce formula, I haven't been able to take away the bottle since, apart from through the night.

Baby is 10 weeks old tomorrow and has started sleeping 7-7.5 hours straight. So I have some questions:

1) will my milk supply decrease when going longer between feeds?

2) should I express between feeds? If so, should I empty my breasts or just pump 15 minutes or so each side?

3) or would my body just adjust to the new feeding routine? Obviously my breasts are super full by the time he wakes up which I feel is the only time he's satisfied and doesn't need formula.

4) would you recommend fenugreek?

I love breastfeeding and I'm so not ready to stop yet, so as much as I'm loving the extra sleep, I'll do anything to keep my supply.

I know breastfeeding as much and as often throughout the day is supposed to maintain/increase milk supply, I've tried and tried but it seems to have the opposite effect, my breasts become completely empty which results in an upset baby ☹️

Thanks all x