At the start of Dec. I was diagnosed with Mono and I'm wondering how probable it is for my boyfriend to have it, considering he still isn't showing any symptoms... He was also potentially exposed to mono around 5 yrs ago, but didn't get it as far as he knows.
The incubation period for mono is 30-40 days on average so it may be too early yet for your boyfriend to show symptoms. Lots of people do have antibody protection to the viral causes of mono because of previous exposure, but never may have been very ill from it, so he may not get sick at all.