Could I Be Pregnant? Community

Concerned that I may be pregnant, though I really have no reason to be, I guess. Maybe I'm just paranoid, but ever since I thought about it I can't get it out of my mind and am terrified that I might be.

I'm 19 years old and am on birth control that I make sure to take religiously at the exact same time every day. My boyfriend and I also use condoms every time we have sex, and we've never had any accidentally breaking. I got my period on December 4th as expected (today is December 21) and had some pretty heavy breakthrough bleeding on November 26.

Since I started on my birth control pills, my boobs have gotten way bigger than they used to be, but that was just about the only side effect of the pills that I've experienced.

Within the past few weeks, however, I've noticed that I'm gaining some weight in my stomach. I'm 5'3" and only about 103 pounds normally, and I'm used to being able to see my hipbones a bit when standing up, but this is no longer the case. I have definitely been eating more than usual in the past month because of more frequent smoking of marijuana than usual, so it could just be from that. But the only reason this concerns me is because the weight is in my lower stomach. I'm used to being able to eat whatever without gaining a pound or looking any different, so this is why I'm worried. It may well be that I just need to cut back on the eating, but I'm still nervous that I may be pregnant. Could this be possible even though weight gain is my only symptom?