Hello and welcome to the club! Not one anyone of chose to join but s@#t happens and life goes on.

Good to hear that you are testing a lot and have your number under good control. Have you read Think like a Pancreas or Using Insulin yet? They have a wealth of information about your new life and the adjustments you are making.

In the lead up to your dx your body was not able to use the energy in the foods you were eating and a lot of those calories just spilled out in your pee. You ate but we're still starving. Also since your BG was high you were becoming dehydrated as your body tried to compensate. If you were in DKA at diagnosis this can be very pronounced.

When they rehydrate you and replace the potassium you were losing you regain the water weight you lost. You also more than likely lost some muscle mass in the weeks to months before diagnosis.
Since you had been wasting calories if you continue to consume the same number of calories as before dx you will put on some weight as you rebuild.
With MDI and basal insulin you will be able to use or store all the calories you are consuming. One thing that is very important to maintaining a stable weight is to be sure that your basal dose is correct and that you can go for 8-10 hours with just your basal insulin and no food and not go low or go high. Your number should not change more than 30 points up or 15 points down during that time frame. Both of the books recommended show you how to do basal testing. It is important to get this right cause coordinating then your insulin to carb ratio and correction factor will be wrong as well. It is important to know how to do this as things will change with time, exercise,illnesses etc and you will be doing this periodically as life happens. No ones T1 is ever the same as the next T1 and what you do will evolve over time.

Once you get your doses of Long and short acting insulin right then you can start on the exercise equation. A good books to read are Your diabetes science experiment and the Diabetic athlete Handbook. You will have to workout when you eat and dose in relation to when you workout. Also the type of workout will effect what you need to do to stay in a safe range.

So short answer your questions is yes happens all the time. Using just enough insulin to cover what you eat rather than eating to your insulin Will help you get on top.

Also whose calorie and carb recommendations are you using? Many people.find that they do better with less carbs per meal as in 30 or less. It lowers your insulin dose which leads to less fat storage. Good fats and protein are a necessary part of your diet and can be increased with out effecting your long term health.