Hi, I Had Intercourse On 16 Aug 2015 And Had

Hi, I had intercourse on 16 aug 2015 and had used the pull out method was suppose to get my period on 1st sep but got it on 10sept wich was very light wd no cramp (usually I get bad cramp) and which last for only a day..after few days of my period I had cramp,back ache, headache constant burping which I stil hv( i never had burping befor)..my next period was due 10oct today its 25th oct 2015 stil no periods...did home pregnancy test got negative result could I b pregnant..pls rply