No period for 4 months, sore breasts, multiple neg tests, could I be pregnant?

[Suzy167]

I am 18 years old and became sexually active with my now ex boyfriend around a year ago. Please keep in mind I've always had irregular periods. We were always super careful (using a condom and the pull out method at the same time). We had sex around 3 or 4 times a week with no complications with the condoms. After a few months of having sex my period stopped and I got super sick with pregnancy symptoms, after 2 or 3 months of no period I was hospitalized for chronic pancreatitis and complications with my liver. While in the hospital being treated I got my period and the worries were gone. I began taking prednisone for my pancreas issues and I maintained a regular cycle for a few months. After I stopped the prednisone my periods just stopped, my boyfriend said he had noticed my breasts getting a bit bigger and they felt very tender. I took multiple tests and they came out negative so we were a bit relieved. I looked up ways to induce period and I started taking 6000mg of vitamin c a day in attempts to start it. I tried with twice and both times nothing happened. My last period was on September 14th and now its December 31st and still nothing. I have taken a pregnancy test at least once a month and they're all negative. I noticed ive been getting headaches in the evening and a little nauseated, no notable weight gain but I have had multiple people comments that my breasts look very large. They are constantly sore and tender all the way around and ive had to buy new bras because my old ones don't fit anymore. Around a month ago I had a new sexual partner and we just used the pull out method which resulted in a very painful UTI and hymen tears. I received a pelvic exam and my doctor told me my cervix looked a little irritated. Would she be able to tell if I was pregnant? Could I be pregnant? I'm very scared because I wouldn't want to keep the baby.