Hi My Question Is I Think Im Pregnant.my Last Sex

Hi my question is i think im pregnant.my last sex was on oct 16 and 2 days after i have my menstruation but scanty.. A few weeks after i feel pregnancy symptoms but was told that i have uti. On nov 20 i hav period but still scanty. My tummy gets bigger and i still have symptoms. I tried pt and ultrasound but all were negativ. Am i really pregnant?