Please slow down. Don’t continue accusing your boyfriend until you’ve had a retest. These tests aren’t 100% reliable. It’s possible your test results are a “false positive.”
Secondly: You didn’t mention how long you’ve been with your current boyfriend or how long ago you had sex with the more experienced guy. Chlamydia is known as a “silent” disease because people are often not symptomatic. It’s possible you were infected some time ago. Talk to your OB/GYN about the course of the disease and what to do about it.
I’m glad you are working on being more trusting. As you know from experience, being undeservedly distrusted ruins a relationship. In order to have a healthy relationship, both people in a couple need to trust and be trust-worthy. Trust is the most profound gift people can give each other. That’s why it is so painful when trust is broken.
Please gather facts before making conclusions. Your boyfriend deserves the benefit of the doubt. If he is, in fact, “innocent” it’s an important lesson learned in the importance of not jumping to conclusions.
I wish you well.