I wouldn't worry if i were you....although that's easier said than done as a mum! Ella is 17months and only weighs 9 kilos. She didn't get teeth til 8 months (still only has 7) - but got 4 in one hit! Didn't crawl til about the same age and only began walking 2 months ago. I didn't want to begin solids til after 6 months also - but she fed really well and her weigh gain was slow but gradual (it didn't go backwards). She's hardly on the weight or height graph but our peadiatrician isn't worried as she has a good and varied diet and puts it down to her having a small frame (like me). When i was 12 the family pead said i was the average weight of a 4 yr old - ridiculous but true - but i was healthy and that's all that mattered.