This thread has great shopping suggestions BUT if you want to stop dressing "like your mum" I think MrsMerryweather's advice is the best. The answer is all in the style.
If you don't take a little time to really think about your style, you're just going to go to different shops and either buy nothing or, alarmingly, buy stuff that still makes you look like your mum!
It's so hard after you have dc because your style does change and your life, and the way you evolve your style changes too. Think about it - when you were younger, you went to school and hung out with loads of people your age, and then again in your early twenties. All that time, you were picking up style cues - what to wear, what not to wear, what was sartorially acceptable in your circle, what wasn't, and so on.
Now it's different - you have a changed identity (slightly) but no really large group to work that out in ... hence the "dressing like mum" default - which makes very few women happy.
So ... change your shops (and this thread will help) BUT also buy/look through some magazines and think about looks that appeal and you could carry off. Think about which women you see (out and about/in films/in picture) who appeal and why.
Hippy is a good look BUT if you are now a 16 on top, you're going to have to go for a slightly more dressy hippy look. Actually, you're going to have to go for tighter tops - just for starters - because otherwise you really will look like a tent. If you go for floaty on top - the bottom half will have to be tighter. 'Tis unfair but a change you must learn to live around. So, go google pix of sienna Miller from a few years ago and see if you can update the look for you and for now.
I keep pushing the slightly prim/vintage look - just because I think it works well for those of us with [sigh] a slightly larger bust.
And I do love Easy Living's style section.