With the exception of DP it's non of their business, why on earth do work colleagues and all, but very close friends even know?
I'm afraid I'd tell them to fuck off, it's on of their business.
As for DP, why does he want you to stop? If you co-sleep still get woken at night, I can see him having a problem, otherwise it's a non issue.
If he doesn't like other people's reactions he needs to grow a pair and support you!
If he finds it hard to reconcile breasts for feeding and breast for sex, he needs to grow up. Breasts are very clever, they can feel sexual when being kissed by a man and friendly and special when fed from by a child, it's quite a different feeling. It doesn't matter if the DC is 8 weeks, 8 months or 8 years old, there is nothing sexual, nothing for a partner to be any more jealous of than mum and child having a hug.
Oh and it doesn't make the child more babyish. DD2 is the most sociable, clever and mature child your ever likely to meet.
(My never EBF, have up totally by 5 months is the odd quirky one)