Hi STOSHUMALA17, are you eating all the meals in the day at the bf's house? If you are eating only 1 of the meals of the day there, you can adjust the intake at the other meals during the day when you are not surrounded by food. Take 1 day at a time and see how the whole day's worth of meals is going. Just 1 meal won't make or break your whole day.
However, if you eat most of the meals there, you might want to take your own salad along. Start your meals with a glass of water so you don't feel too hungry.
Or cut down on the portion sizes of the meals that you don't consider healthy. That way you eat with everyone but in healthy amounts.
Carry some healthy snacks with you to fill you up later so you don't undo all the efforts you are putting in.
If you were doing well with exercise and eating already, you can do it again. Involve the family by going for a walk together or eating a healthy snack together and help them see a healthier life as well instead of you falling off the wagon.