Why is it so hard to lose weight!!!!

I’ve been trying so hard to lose weight counting my calories and exercising (30 minute cardio)I had my baby now 8 weeks ago through csection and having a hard time losing weight, my husband in the other hand loses weight like nothing without trying I just wish I was more like him after having my kids it’s so much harder to lose weight,when I was younger it seemed so simple now I try and still have a hard time, any tips? I’m trying but can’t seem to get the weight off