Pregnant after a vasectomy? Pics.

Can any of you tell me what you think? My husband had a vasectomy in September, 2018 just 5 months ago. He never went back for his 3 month check up. We just assumed it worked because we weren’t using protection, and I never got pregnant. Well, I’m 2 days late and decided to test. I have irregular periods anyways so I just did it for the fun of it. I’m having lower back cramps like usual before my period, but I know I see a faint 2nd line. I do plan to re-test if AF doesn’t show up in a couple days. Would it even be possible for me to be pregnant if he had a vasectomy? Any thoughts or stories from you ladies would be appreciated.