What Causes Tightness In Vagina?

Hi, i am seventeen and my boyfriend and I have unprotected sex, we've had a couple of preganancy scares, but as of lately my vagina has been tighter, and my partner tells me how my vagina and semenor "cum" taste different, ive had backaches, hightened smell, cramps, bloating and its not even close to my menstruation date. I am wondering if i could have a bladder infection again or if i could be pregnant. My partner also says that i have been abnormally tight. Any answers?