The reason you lost weight was because your body was starving. Even though you were eating, there was no insulin to allow your body to utilize the nutrients in food - therefore it was like you weren't eating at all. Now that you have insulin in your body again, your body is efficiently breaking down and storing the food properly. Insulin is a fat-mediated hormone meaning it needs body fat to work properly.
You can still maintain your weight and even lose weight. Weighing yourself every day is not a good idea because everyone's weight fluctuates from day to day depending on the food ate, fluids consumed, and exercise. A lot of the weight gain you are seeing can also be water gains. You probably became extremely dehydrated in the days before your diagnosis, so now your body is also replenishing its water stores.
There are simple tips to remember for weight control: eat regularly and consistently throughout the day so you don't allow yourself an opportunity to feel super hungry then overindulge in foods, keep healthy snacks available, and rather than eating straight from the package - measure out single servings and put them into plastic baggies. Consume foods high in protein and fiber to help keep your belly feeling fuller for longer and drink plenty of fluids (no calorie ones like flavored water are great). When having to choose between multi-grain and whole-grain, choose whole grain.
And exercise regularly. Exercise is tricky because it also messes with your blood sugars and insulin needs, but with careful checking, as well as with practice, you can easily work exercise into your daily routine. Park in the back of the parking lot instead of at the front. Take the stairs instead of the elevator or escalator. Walk around the house or do jumping jacks during TV commericals. Take a walk around the block during your lunch break. Exercise doesn't have to be difficult or make you incredibly sweaty. Just keeping your body moving is key.
A lot of people eat when they aren't hungry. Really pay attention to your body. It will tell you when you need food and when you've had enough. When you are feeling bored or sad or emotional, distract yourself with something other than food - going for a walk, watching a movie, or participating in some hobby you enjoy.
And also - don't focus on all these things at once! Adjusting to life with diabetes is difficult in itself - making one small change at a time will help you turn these changes into permanent lifestyle behavior. Instead of doing everything at once, set a small goal for yourself you know you can consistently accomplish. Once you have regularly worked it into your daily life, move on to adding something different. Changing your world doesn't have to be stressful or difficult. It needs to be manageable otherwise you will never stick with it - becoming completely overwhelmed and throwing it all away.
We are here to support you and help you! Keep coming to us and we will help you get through the rough patches :o)