Boyfriend had vasectomy but I am 5 days late.?

I'm 24 and my bf's 31. He had a vasectomy after his daughter was born 3 years ago. We've been having unprotected for 3 months now, and this month I'm late and usually never am. I had cramps and verrrrrry light spotting a few days ago, but that is it. His ex never got pregnant again after she had his daughter and he had his vasectomy. What are the chances I am pregnant? I've had a few pregnancy signs like nausea, bloating and swollen . I don't know if he ever got his sperm count checked after the procedure, but I figured it was successful since his ex never got preg again. Anyway, any insight? I would love to have a child with him someday, and he's considering reversing it...but what is the chance I'm pregnant now?