Hi, Chelsea. I’ve been alerted to this thread as in the past I have contributed quite a lot and maybe I can help. I’m a former BFC.
It is good news your baby has gained weight. You’ve had a hard time since the start, from what you say - poor support and confusing info. Some of the replies on here are a bit contradictory and sometimes incorrect though obv all well meaning. Your head’s prob been spinning.
When babies don’t gain weight as they should, there’s usually no underlying issue, though it’s always good to check that out in case there is. Usually, it’s a question of milk intake. If milk intake needs to increase then obv formula or expressed is an option, if I take can’t be increased quickly by direct bf. Expressing is difficult for many, and this is where formula alongside bf can help, as you’ve found.
If you’re keen on continuing to bf, then it will be important to have a plan. It’s not correct that giving formula at this stage will not impact on your supply. Breastfeeding needs to happen a lot - prob 8 times min in 24 hours. Both breasts at least once each time - it’s called ‘switch nursing’ and you can look it up. Some of the info on foremilk and hindmilk on this thread has been wrong, I have to say. Don’t be too hung up on it - feeding often and effectively is the way to go.
More than this, though, it’s good to get one consistent informed person on board to help. I’d suggest an experienced BFC or a lactation consultant, someone who knows about bf challenges and who can also gauge if your baby needs a clinical assessment, too.
Post again if you need help to find someone like this if your HV or other local contacts can’t tell you.
Best of luck. Armed with a plan, and support, is best 😀. Too many voices, inc mine, are less likely to give you the right help at this stage, I think.