Does your body or hormones change a bit after someone becomes sexually active?

Okay, so my boyfriend and I have just started being sexually active and are using protection when we have sex, (the only exception is when he just fingers me and all that), but about 2 weeks ago, his penis went a little too close to my vagina for my liking (his ejaculation after I gave him a ha****b kind of went on my inner thigh, but he wiped it off with his shirt and he wiped off what was on his hands too). And so now I'm not sure if the symptoms I've been experiencing are possible pregnancy symptoms or just my upcoming period. Some symptoms of mine are:-Lower back pain-food cravings-getting gassy-fatigue (more often than usual)-having to pee more often

it's weird though because these symptoms came up right after we finished fooling around and stuff, which is making me think that no, I am not pregnant. but still! I looked up these symptoms and most of them also involve early pregnancy signs which is making me super nervous. Can anyone tell me if I'm pregnant or not? And also most of them I've only started experiencing now after I've become sexually active. 

Oh and I've been checking my cervical mucous too. If you have had conceived and were possibly pregnant, could you have a dry spell? because that's what I'm having and I read somewhere that when you're pregnant, the mucous usually becomes more. Also, does your body or hormones change a bit after someone becomes sexually active? I'm 80% sure I'm not pregnant, but there is that 20% that's keeping me up at night.