My stomach feels hard and full-like all the time, is this a

It's been a little over a month and I've been feeling skeptical about pregnancy. I don't know if I've missed a period because I'm on a three month cycle with my pills. I even had my period before that for a month. Sketchy.

So, for the past week I've noticed that my stomach feels tough when I'm standing up and even my friend says it feels weird. Not only that, my stomach feels full. Like I've had enough to eat.
I drank alcohol last Thursday and I had sharp pains in my stomach near my belly button and some chest pains as well. I didn't even get drunk and I had a few shots and then some mixed ones as well...
Other than that, I haven't noticed much of anything else, can't really tell if I'm peeing more than usual or any changes in eating habits. My breasts have been a little sore but when I started on my new birth control this summer they started to ache and then grew. I lost weight and so they seem to be smaller, but now they ache again.
I don't know.
I just wanted to know what someone else thinks before I spend money on a pregnancy test.
Any ideas?