27 weeks and PISSED!

Today, my fiancé of 3 years and father of my two year old son denied our unborn child! Told me to my face he has doubts that this baby is even his!

Background:

Right before I found out I was pregnant FIL had a stroke and I took leave because MIL was keeping our son. Turns out MIL decided she didn't want to keep our son anymore (no big deal if it wasn't three months later and I was clearly showing) we agreed it would be better if I stayed home since me working would only pay for daycare. So I've been sitting at home everyday since then. I've gotten to the point that I scrubbed the baseboards of the house due to boredom. My son definitely keeps it interesting around here but he also likes his space to play alone (boo)

For some reason my fiancé has been questioning me on things recently. Things like who I'm on the phone with, what I did that day, who I've talked to, why I decided to fix my hair every once in a blue moon, etc.

Today I told him I wanted to get a pedi and get out of the house for 40 min for me time. His response "why would you need to do that?" WHAT?! I asked him what it was he thought I would go out and do at 27 weeks pregnant. Prostitution? Drugs? I just wanted to treat myself. All of a sudden he started freaking out and said, "honestly there is no telling. You brought that up. Who knows at this point that baby most likely isn't even mine!"

I have never cheated or even thought about it. I haven't had any suspicions of him until now but my biggest issue is why in the hell he would wait until I'm this far along to speak up. He's been to almost all of the doctors appointments, but had been a little distant. The only thing he really engaged in was name picking.

So here I am, in the living room stuffing my face and binge watching tv going on the 3rd hour. I haven't said anything to him since he got home. He hasn't bothered to say anything either. What should I do? Leave? Talk to him? I'm completely lost and so hurt... not how I wanted this to go at all!!