Simple question and ten points for u?

last month i have done four times sex with my boyfriend ( unprotected) and after that i felt some symptoms like urine burning, bad smell from vagina, frequent urination, itching of vagina after or during urine and lower abdominal pain, and missed period, i felt that it is std so i went to pharmacy, bought some medicines,(for a try, without testing that it is std or no) now all symptoms have reduced but still my period is late. even i have tested pregnancy but results are negative, so i wanna ask the symptoms have reduce, no pregnancy but still late period? y ? so?