Why i can't be pregnant?

Me and my live in partner for four months we had sex everyday once in a day. We don't use any protection. he blow inside of me everytime we make love. we were in 1st year anniversary. we make love when we meet always. we never do withdrawal and never use condoms etc. but why i can't be pregnant? in one year i missed period of 1-2months i took pregnancy test because i thought im pregnant but it's always false alarm. my friends suggest that i should visit a ob gyne but im scared of the result. And i have no time too. is this happened to other girls here?