My Boss' Wife Could Not Get Pregnant For Him, Now He's Got Me Pregnant

I work in this office and my Boss and his wife have been married for about 11 years without a child and the wife filed for a divorce not too long ago. We started a relationship when he came down about a year ago and wished I could get pregnant for him. 

We use to have unprotected s*x a lot but I didn't see any sign of pregnancy so I concluded he may be the one with a problem, hence his wife's decision to leave him. We decided not to have s*x again on the 1st of January as we both feel guilty after the act.

Now there is a problem...

I tested positive when I checked with a test strip, so I'm pregnant.  He's very happy but I'm not. He told me he wants to go and see my family and have the necessary rites performed in March. 

My worry is he might not do so (as promised) and the pregnancy will start showing. I had the same problem with my first son's dad who always postponed the date for him to come and do the traditional rites till my tummy grew and everyone noticed I was pregnant yet he didn't marry me.

I suggested an abortion but he refused saying I'm depriving him of becoming a father besides he's getting to 40. If he end up not marrying me like my ex, my family will be very disappointed in me for allowing such happen to me again as I can't call this one a mistake. 

I'm so confused and need your advice on what to do. Can I trust my boss?