Contracted chlamydia but unsure how?

Recently I was diagnosed with chlamydia after testing and was unsure how I received it. I’ve only had sex with 2 people in my life. After the first relationship I was tested and was negative. Since I’ve been with my partner I’ve been negative and so has he. The only rational thing I can think of is when I had a surgery 6 months ago and was medically put under and possibly SA’d? When I found out I had my partner test and he was negative- which is surprising since we’ve had sex recently multiple times which would make you think he would have it. He couldn’t have faked his results since I did see him pull up his my chart and show me. But back to the surgery bit. I was medically put under and 2 months after I went to the hospital again since I was having sores and really bad pain in my mouth which turned out to be herpes. Not sure if both of those go together. I’m really confused on how to go about this since I have no idea where I got it from and I’m either thinking I was assaulted during my surgery or if my boyfriend had it, was medicated for it and hid it from me.
EDIT: I understand the SA part is insane conclusion. But I myself find it so very hard to believe that my partner would cheat on me. I am also going to clarify. NO I did not cheat on him. I work almost 60 hours a week and barely have time for myself let alone having time for someone else other than my boyfriend.