Don't take offense I have pcos I lost weight and my periods returned the more weight I lost the more frequent they became until perfect on time :)
Irregular periods are normal for women with PCOS. I'm not sure what the significance is about the event with your boyfriend, but from that alone, I wouldn't assume anything related to your missed period unless you're concerned about an STI. I would suggest going to your Gynecologist and discussing how long it's been since your last period. They may run a blood workup and possibly have you do an ultrasound to see if there's a build up of cysts. As the first respondent mentioned, weight is a big factor with a woman's period, but in addition to that, the fluctuating hormones of someone with PCOS is an even bigger factor. One of my doctors tracking me for diabetes (which is a common symptom of PCOS) placed me on Metformin and that kept me regular. Birth control is another useful option to have regular periods. My favorite birth control pill were the Trinessa 28s. They were super gentle on my body and even kept the acne at bay much better than other pills I tried in the past.