I'm scared..

I'm scared I could be pregnant.... Last time I had sex was around 5 weeks ago. I'm.on birth control pills and I'm taking it at the same time every day. But it's not 100% safe, is it? I had my AF as expected but it lasted only 3 days which is not that unusual because of the pills. But recently I've been having little cramps. actually, not cramps like during your period but like when you are hungry or when you've been running for a long time. Like stabbing. Once I also got drunk really really much (not sure if that has something to do with that). And I'm peeing a lot these days. I wonder if the pain could be from stress from school. Sometimes I have a little nausea especially after coffee. It's Christmas so I ate a lot so this all could be cause just by my stomach maybe. I don't know but I'm bit worried. Do you girls have any advice or idea what is going on??

..I'm 19 and definitely not ready for child..I can't even take care of a dog