I want to loose weight

Georgia
Ladies, I hope you can help.
I'm around 230lbs and I'm 5'7, it works out that I'm 3 stone over weight.
I'm absolutely petrified of weighing anymore than I do and I would love to loose weight before the baby is born, I'm only 5+5.
Please can I have some advice on what I could do to lose weight? I've been healthy eating for some time now but what excersises are good? 
Thanks in advance x