Telling truth about disappointment

Yesterday my bf and I were in bed together and chatting. We'd just gone through a pregnancy scare after I took plan b 48 hours after the first time we had unprotected sex. He admitted that he was a little disappointed that my pregnancy test yesterday (9 days late) was negative. I was so shocked that he said it and told him I was quite disappointed too. But I think I'm angry at myself. I took plan b because I thought I wasn't ready for a kid and he never wanted them. But the pregnancy scare told me that I really wanted it. I feel like I should tell him the whole truth but I can't. I know that he wants me to be pregnant because he's attracted to pregnant women and I don't want him to think that I'm crazy for wanting a baby as we're only 17. I think he's still hoping that my period won't come for the second month in a row.

Edit: essentially does anyone have any advice on how i should talk to him? I'm thinking of waiting until a couple of days after my next period is due.