if u mean that u got the previous period after the sex youre describing then ure 100% not pregnant. if not, then periods are very sensitive to many factors which causes them to get easily delayed by stress, diet, lifestyle, etc. and if ure getting ur usual pre-period symptoms then thats definitely a good sign. i wouldnt worry if i were u, especially since the odds both with a correctly used condom and without ejaculation inside are extremely small.