Baby not walking ..

My son will be 14 months old tomorrow and he still isn't walking. He's standing on his own a lot more and for longer and he'll take a step here and there but no significant walking. His doctor said that if he doesn't walk by his 15 month apt (sept 26) then they'll start evaluating him. I know he wants to walk cause when he'll stand he looks like he's thinking about it but then he'll lower himself down and sit. As his mom when I heard "evaluate" I immediately thought there was something wrong but I know there isn't. I just need advice! When did your child start walking? What did you do?