My DS took his first steps at 16 months - one month before DD was born, so it was hard work being heavily pregnant with him not walking. I thought he was quite a late walker (about 4 months later than the last of the other babies in my ante-natal group), but DD was much later. She started crawling at 14 months (she didn't make any attempt to move around by herself before that!), but she wouldn't bear any weight on her legs with me holding her until she was 18 months old. She stood up for the first time holding onto the sofa when she was 20 months old and walked for the first time at 22 months. She was never a really a 'toddler' - she went from walking to running very quickly, and by the time she was two, no one would have guessed that she'd been such a late walker. She has never had any co-ordination problems - she loved ballet when she was little and then swapped to gymnastics when she was 6. She was a British Championship level artistic gymnast by the time she was 13.
DD was (and is still at 17) a very healthy, robust child who only went to the doctor's surgery for her vaccinations and saw the health visitor a total of 4 times after she was born (the last was her 8 month check). The health visitor was slightly alarmed at DD's 97th percentile weight at 8 months, but she wanted to tick off all the 'milestones' on her checklist, so she was much more concerned by DD's lack of interest in crawling and her inability to bear any weight on her (very fat) legs. Fortunately, as DS had been a fairly late walker, the HV left it up to me to monitor DD and asked me to arrange a follow-up visit if DD was still not bearing weight on her legs by the time she was 10 months old. Two months later, there was no difference, but I wasn't worried about DD at all, so I decided not to get back in touch with the HV. I knew if I did, she would start arranging unnecessary interventions and DD was still only 10 months old. The HV probably just ticked the 'weight bearing' box on her 8 month 'milestone' checklist when she didn't hear from me. I'm sure she would have been horrified to know that it would be another ten months before DD finally put her feet on the floor and held her own weight with me supporting her! There was never anything wrong with DD, she was just overweight (from a healthy appetite and a lack of movement) and very lazy.
Children develop at their own rate and there is such a wide variation on 'normal' for achieving all the various 'milestones'. My DS didn't really talk at all until he was 3 and then went straight to complete sentences. He wouldn't feed himself (even with finger food) until after his first birthday. He was still on the first level of the Biff and Chip books (with the three letter words) in the summer term of Reception, despite being a September baby and one of the oldest in the class, but by the age of 7 he had a reading age of 11.
DD might have been very slow to start moving herself around, but unlike DS, she was a very early talker (I used to be able to have conversations with her about her not walking yet!). By 6 months old she was holding her own Tommee Tippee cup and feeding herself finger food (I know it's disapproved of these days, but I started weaning both DC at 16 weeks and they were eating the full range of Annabel Karmel recipes by 20 weeks).
DD and DS are now 17 and 18 (lower and upper sixth) and are both healthy, sporty and academic. There is no difference at all between them and the children of the friends I met in ante-natal group, who met most of their 'milestones' much earlier than my DC did.
Sorry, that was a longer reply than intended it to be. I really just wanted to say, try not worry or to let any judgy comments get to you. He will get there in his own time and there's no rush.