Does Generic Birth Control Pills Have Side Effect Of Weight Gain?

It is about birth contol.
I was on a birth contol that seemed to work good. The doctor asked if I would be ok about switching to a generic brand then that way the pills would be sent straight to my house. She ensured me that they were exactly the same. I agreed. I haven't been on them long, not quit a year but I have noticed weight gain. Pants getting tighter from when I wore them in Oct. Another pair are getting tighter from when I wore them just this past Feb. Could it be because it is a generic brand? My eating habbit isn't bad but maybe not the greatest. I try to eat a yogurt or a meal replacement shake for breakfast. Fresh strawberries and ganola bar or yogurt for snake. Lunch which could be Subway or yes Taco Bell. Another small and healthy snake and then dinner which is a steak, greenbeans and a baked potatoe, or bbq chicken, or soup and grilled cheese. I try to eat small portions. I watch what I eat a lot. I take vitamens. I walk alot for work, on my feet all day. Walking up and down stairs daily. Hiking up and down hills once a week usually. I try to walk my dogs at home and usually running around for my son. So I feel like I am not an unhealthy or lazy person but seem to be gaining weight. I want to loose this weight to help my self esteem and mood. I can't afford 100.00 a week for meals from some of these diet plans. I am trying diet pills but not satisfied yet with them and it has been about a month. Please help me. I want to feel beautiful inside and out!