A bunch of strangers online cannot tell you for definite what is going on, or not going on, in your uterus. You either need to take a pregnancy test, or see your GP. From what you've told us, you're highly unlikely to be pregnant. Stressing about things can delay periods further which isn't helping you to not stress. Also, you said you were pressured to have sex, were you pressured by your boyfriend or by other people?