You are totally not pregnant. Don't stress about it any longer, OK? You are nervous and so you are feeling every little thing about your body and thinking it is connected to this episode, but it's not all connected.
To get pregnant, sperm MUST enter the vagina. It really cannot do so through clothing. About the only way this ever happens is when a couple is both in their underwear and the penis actually does touch the vagina during ejaculation.
Also, whenever we have a period, that means we cannot be pregnant. A period is the uterus shedding the lining that it had built up in case of pregnancy. If the uterus is shedding that lining, it cannot support a pregnancy. So even when a period is late, it's still a period and it sill means no pregnancy occurred.
So relax, OK? No more stress? And before you and your boyfriend go much further in the undressing area, consider having condoms on hand just in case, OK?