Teen sex

I’m 17 and I’ve been having sex with the same boy since I was 14, we’ve been broken up for 3 years but we just started recently having sex again in October. I’ve had 4 sexual partners since me and him broke up in October 2016. My last partner was on November 21st, and we didn’t use a condom. I got a call from my doctor this morning and she said I have chlamydia. The boy that I’m consistently been having sex with was tested on the 8th of November and he was clean and he doesn’t know about my other partners. So of course I go to the other boy that I recently had sex with and he said that the last time he had sex was in February. I talked to my ex and his mom about it and he said he hasn’t done anything with anyone else in months. I feel bad because I want to tell them about my other partner but I don’t want him to get mad at me but I also don’t want him thinking that it’s his fault. I’m also wondering if urine tests can be mistaken for chlamydia?