Early days in adoption are hard going - it’s not at all like giving birth, where you’ve carried the child, prepared for them physically and emotionally and really nothing can prepare you. Bonding, in the best of circumstances, takes time - many birth mums struggle to bond with their babies so it makes sense that a bond with a child who is effectively a stranger to you would take time and effort.
It’s also very usual for children to regress significantly in early placement. Every thing in their lives has changed, there are no familiar people, smells, sounds, no familiar house rules. So they regress to a younger age - things like toiletting, bathing, eating, sleeping, speaking all are up for grabs. I’d not worry too much at this stage - you aren’t seeing you’re actual child at this point, you’re seeing your scared, uncertain, traumatised child.
Everything has also changed for you - your understanding of parenting needs to shift to accommodate this little one, you have a complete change in family dynamics and are back to being tied in a way that you had perhaps moved away from. It’s not like adding a birth sibling, which is often more tricky than people want to admit. I imagine you feel quite deskilled in it all.
So, first off be very gentle with yourself, and with your new child. Don’t worry about routines and what normal family life is like - you’re not in a normal situation. Go at the child’s pace, your DH will need to do the heavy lifting with yourself birth child while you get to know this new little one. I’m guessing he’s been doing all the fun stuff while you’re trying to keep the house ticking over, swap some of that so you have the time to attend to your little one. Go out, play games, cuddle watching TV - just spend time with them not trying to do anything productive.Take meal times, bath times, bed times at their pace, split the routine with yourself birth child DH so you both have some down time.
Take yourself out for a walk, or a coffee, or to see a friend - get some respite.
Do things with your new child that focuses on relationship, chatter to them through the day, don’t worry about bonding, or attachment or anything else at this stage, just get to know them.
Keep an eye out for any continued development issues, and yes delay the adoption order until you have an idea of any ongoing issues but it’s far too soon now to know what those might be.
And keep posting, if you give an idea of the ages of your children or things that are particularly difficult there are many very knowledgeable, experienced adopters here. I can guarantee you someone here will have dealt with the things you’re finding hard, and folk here are very generous in sharing their experiences without judgement.
You’re finding it hard because it is very hard, but for most of us it does get better.