I would say you're at a healthy weight right now, but I know how it feels to be self-conscuous about your body. In all honesty, the only way to keep weight off is to cut calories - exercise can help, but unless you do it on a very regular basis, you won't keep the weight off. Eating healthier and a bit less can help you in the long run.
For example, if you normally take in 2000 calories a day, try cutting back to 1500 a day. Doing this, you could lose a pound a week, even if you do nothing but sit on your duff and watch television all the time. How's this work? Very simply: 1 pound is equal to 3500 calories. 500 calories a day x 7 days in a week = 3500. If you want to really go nuts, cut out 1000 calories a day - eat lots of lowfat or nonfat foods so you can stuff your face silly and not take in a sickening amount of calories. Drink lots of water because water will make you feel really full and will discourage excess between-meal snacking.
But, since this topic is in the getting pregnant forum, if you are indeed pregnant, don't follow any of what I said at this time in your life. You should actually be taking in at least 400 extra calories a day for your child and doing maybe a little bit of light exercise.