What is wrong with me?!

I can’t lose weight for the life of me!! I’ve gained about 30 pounds over the last 6 months and it will not. come. off. I’ve tried cutting calories (not extreme, but keeping it in check), cutting out soda, I go for a 30 min walk everyday, I only eat out maybe once or twice a week now (it used to be almost daily), and I just keep gaining weight. What is wrong and how can I fix it??