Iud unprotected intimacy but growing belly ???

Star
Hi I have the iud inserted I have had numerous times of unprotected intimacy ... But for the past few weeks I have noticed my bottom belly growing last time I saw my belly growing like this was when I was pregnant with my first child. I did do a pregnancy test a few weeks ago but negative ... However I look pregnant and sometimes I feel nauseous..;( hoping I am not pregnant any advise out there ... ??? Help!!!