I'm 18 and I don't know if I'm pregnant? Helpp!!

I had sex around the weekend of January 7th, and we used a condom and didn't even finish. I've been having a hard time sleeping for weeks and I've been having some back pain. But since about a week ago I thought allergies just hit me but my mom thinks I'm sick. I do have sore throat and coughing, but I've had morning headaches, shortness of breath, and rapid heart beat along with a slightly elevated temperature. I've always had small breasts but I went from a 32 A that I've always had to a 34 A quickly and they're slightly tender. I've also had a LOT of vaginal discharge for a couple weeks and for about a week I've been eating twice as much and have been urinating quite often throughout the day. The odd parts are that I'm still having the menstrual blood and cramps and have no tummy either. I've always had periods lasting about a week with bad cramps for the first 2 days, but the monthly periods I've had since I had sex are about 4-5 days long and the cramping can last 3 days and are EXCRUTIATING! Then I heard some girls don't get bellies. I have felt frumpy and feel like I'm getting fat, but I still fit in my size 1 jeans and everything. I'm so confused and just want to be on the safe side. Could I be pregnant?