Just make sure you eat enough calories per day...your baby needs them to develop correctly. Pregnancy isn't the time to diet, and trust me, I share your concern. I had dropped about 30 pounds, and now I'm likely going to gain most if not all of it back. Just eat right, exercise as well as you can, be heathly for your baby...but don't restrict your calories right now. Avoid the ice cream, eat lots of fruits and vegetables, lean meats, healthy milk products, whole grains, etc., I'm sure you know the drill. You can talk to your OB about what might be a good caloric intake for you.
If you breastfeed I've been told you tend to drop most of the baby weight and then some, and if not, running after a toddler should do it lol. Just kidding, but you know weight loss is as much about knowledge and determination as anything, if you did it once you can do it again.
It's definitely possible to maintain and gain a healthy weight while pregnant. Your pre-pregnancy weight will influence how much weight you will be expected to gain. It's important that you keep hydrated, and that you do not cut or skip meals. Some things that can help are not eating past 9:00 pm, maintain portion control, eat fruits and vegetables, limit (or completely cut out) soda and caffeine, regularly walk and keep active.
I'm kinda in the same boat..I started a healthier diet and exercize last Jan too..I've lost 42 lbs since then but have gained 5 back since finding out I'm pregnant!! Due in July..I'm 12 wks..I'm concerned abt gaining a lot of weight because I've been really, really hungry all the time..I'm trying to really stick to only 300 more calories extra a day..I've read that's all you really need to give baby the extra nourishment..but its very hard..I'm trying to eat fruit if I'm really hungry and I'm over my calories..?? ;-)