I had sex with someone different a few days ago, since then i've had bladder/pelvic pain on a constant basis even though i used a condom?

Developing pain: so soon after intercourse suggests infection/prostatitis, but you did use a condom. This would seem unlikely, but probably worth checking out. More chronic pain might suggest some pelvic floor muscle dysfunction or problem. I would first see your doctor to have tests for urinary or prostate infection, and then go from there. Good luck!