Could Delayed Periods Along With Sore Breasts Be Due To Pregnancy?

Hi, I m 30 years old and normally get my period on time. However, last month I noticed it came a bit early. My last scheduled period was December 25th and lasted 5 days. I have been having unprotected sex with my fiancé for almost a year now and we tried getting pregnant to get several negative at home pregnancy test results. My last period was on January 17th and I haven t gotten my period for February as yet. Whenever my fiancé goes to touch my breasts, the nipples are sore and I notice my belly isn t as flat as it should be. My period usually comes every 28 days. Could I be pregnant?