If your dd is happy, healthy and alert with plenty of wet and dirty nappies, have a read about "catch-down" growth: ie a baby adjusting to what its growth curve should be, based on the child rather than maternal health.
Ds was 8lb 15oz at birth, had a massive initial drop (not helped by newborn jaundice and a period under UV lights) took 6 weeks to regain birthweight
, saw a paediatric consultant at 7 weeks (had been referred a couple of weeks warlord but wasn't deemed to be urgent), who was more interested in what my dad (a retired paediatric radiologist and former colleague of his) was doing than the obviously happy healthy and alert baby in front of him. He told me to "stop the faff of expressing" (I'd been supplementing with EBM between breastfeeds from less than 2 weeks old) but just to continue breastfeeding and enjoy my baby 
He explained that ds, who at that point was under the growth curves
but tracking them would eventually move up to probably the 50th centile. Which is what he did.
He's now a happy, healthy and alert 22 year old
- albeit slim and only 5'8"
I continued to express anyway (mostly for the freezer) as I had to go back to work when he was 4 months old and in the end breasted him for 13 months 
Are you and/or your dh small? I'm 5'5" and dh is 5'7" and we are (or were then
) slim.
I'll admit to avoiding seeing HVs but continued going to the breastfeeding support group run by the midwives at the maternity hospital for months. (They we're the ones who advised me to express more for confidence and lent me an electric expressing machine - but it actually made no difference to the rate of his weight gain - and also referred him to the paediatricians, just in case).
I didn't know it was called catch down growth then but it does explain his growth curve, as he adjusted to the curve he should have been on. (I also suspect I had borderline Gestational Diabetes which can also result in heavy babies).
As dh used to say: if my dad (dh's FIL) had had any concerns about his PFBGC (Precious First Born Grand Child), he'd have had him in to see his former colleagues quicker than you can say "Paediatric Radiologist" 