I Am Currently Using The 3 Year Birth Control Implant

I am currently using the 3 year birth control implant and have been questioning wether or not i could be pregnant i have taken 3 pregnancy test all which came out negative. But i have also had recent symptoms like nausea when my one year old trys to lay on my belly or if i lay on my stomach i am constantly exhausted and at times my stomach will become hard and buldge out slightly, my feet kill me after a few hours of walking standing or working and i have had recent blood chunks in my urine. Any advise?