I read your post a few days ago but didn’t have an account to post and your health visitors comments have really been bothering me!
For context I mixed fed my first because of a tongue tie, currently EBF my 4 week old.
My first DS was also on the second centile and I did lots of work with a dietician after 6 months when I introduced him to solids. He went up to 25th whilst working with her and then slipped down to 9th and stayed there. Some kids just are just a bit smaller! He’s now 4 and healthy. However I carried BFing until nearly 3 years, so even if you do choose to mix feed, it’s by no means the end of your BFing journey! If you do choose to mix feed you could do formula with a cup so that your DC doesn’t prefer bottle. Always after you’ve bf though, or you could offer a bottle but use the PACE method where you keep baby sitting up and bottle level so they don’t get the milk too fast. (I found expressing with a new born stressful and time consuming also).
Also, with 10 min feeds maybe he’s not getting enough hind milk? You’d notice this if his nappies are green. I find my DS2 feeds longer in rugby position than he does in cross body. He also has a deeper latch so it’s more comfortable.
It sounds like you could do with some support, are there any BF support groups near you? The family centre should have details, also, they should also be able to provide you with BF support. Other places that could help are Le Leche League, www.laleche.org.uk they have a support line and sometimes a group local to you. If you did antenatal classes with NCT they also have support you can access. And as another poster says, there are some fantastic BF support groups on Facebook. It’s good to have a community.
Lastly, BFing is hard, there’s all sorts of misinformation out there which doesn’t help when you’re a new mum. You’ve done 7 weeks EBF, give yourself a pat on the back, you’re doing awesome mama!
Whatever you choose, please don’t give yourself a hard time. Good luck!