Why am I not gaining weight?

I have been bodybuilding for four months now and have gotten much stronger but recently stopped gaining weight and am not making any progress in the gym anymore.I eat every 3 hours,high protein and carbs,whole grains,eggs,lean meats,fruits,vegetables,nuts,and drink 3 scoops of whey protein a day including one 30 minutes after a workout.I don't eat a big meal so I am thinking I might need to eat more.I workout 5-7 days a week for at least an hour.Cardio 2-3 days a week too.I haven't lost any strength or muscle but I am actually losing weight despite eating every 3 hours.Should I eat more?I drink a casein protein shake before bed too and take creatine after a workout.Please give me good answers.NO SPAM.