I'm A 27 Year Old Male And I Have Purple

I'm a 27 year old male and I have purple dark reddish bump inside my urethra started off on the left side but is now on both left and right side there is pain and discomfort throughout the day comes and goes same as when I urinate and after sex sometimes it's swollen sometimes it's not and looks normal and tell you open up and look inside the urethra then you'll see the small purple bump also looks like on the outside over there you're either looks like lips on each side this too size varies throughout the days sometimes the pain is a burning sensation other times it's more of a sharp pain and it doesn't hurt when I touch it but the pain is definitely there I did have multiple sex partners of which are very sexually active and I know I'm not there only partner I've also gone to the doctor and got in treated for various things and received antibiotics multiple times they tested and both came out negative for gonorrhea and chlamydia please help and thank you for any advice or suggestions