First, congratulations on losing 35 lbs! That's wonderful!!! Don't forget how far you've come. =)
Second, the good news is the 10 lbs you gained is probably not all fat. It would take 35,000 extra calories to gain 10 "true" lbs, and hopefully you didn't consume that much on one vacation! Some of that weight is probably water weight from eating unhealthy foods (and drinking alcohol if you did that). Now that you're trying to get back on track, drink plenty of water (8-10 glasses per day!) and get lots of fruits, vegetables, lean protein, and whole grain, and you'll probably see some of that gain drop off pretty quickly. I don't know about you, but losing a little water weight quickly helps me feel better about myself even though I know it's not "real" weight loss! =)
Lastly, make sure you don't set yourself up for failure by setting your goal too high. 30 lbs in 3 months is possible, but it would be extremely difficult and may leave you deprived, exhausted, and more likely to gain weight back after the wedding is over. Why not scale back your goal a little bit to 20 lbs? Find an awesome dress that fits your new body and celebrate the 35+ lbs you will have lost by then! If focusing on three months is overwhelming and that's what is making you feel blah, try focusing on losing 1-2 lbs per week instead. That would equal out to 12-24 lbs gone, which is more realistic.
You obviously know what to do since you've already lost 35 lbs, you just gotta get back to it. =) I hope you find some motivation to continue on your path! Best of luck!!!