You have 5 months to lose 15 lbs, that's three pounds a month which is very doable. Being you are so close to goal it's not going to be a walk in the park. You will have to be VERY diligent with diet and exercise- having an off weekend can mess up an on plan weekend very easy.
I don't know what you did before but I'd suggest calorie counting- do you happen to know how much you are eating right now while maintaining? I'd do 1200 calories a day with your weight and fill up on veggies and protein as much as possible
Sparkpeople.com is a great food tracker
I'd probably ask in the lightweight section for tips or to see what they are doing to get rid of those last few lbs