I don't remember getting my period can I be pregnant

Jas
I don't remember when I actually gotten my period. 
​I did get my period on June 11th and 28th..
​Then things start getting fuzzy when July hit because I don't think I got my period on the 11th but I know I got it on the 28th or so
​Next, August came and I don't remember getting my period on the 11th and I didn't get it on the 28th which is unsual for me but I also had been having sex throughout august and if I don't get my period on the 28 I normally would get it by the 30th by the lastest. 
​But my thing is I don't know if there would be any possiblity for me to be expecting if I got my period on July 28. 
​Any advice would help thanks