I can't mine anything but the blocks above me!

So I have these 1x1 tunnels in my Minecraft world, and when ever I want to mine anything, it mines the top block instead of the one in front of me.  This is really annoying because when I left before 1.13.0, I was in my tunnels.  Now, I can't get out. This is because I can't physically click on the trapdoors at my entrances. Please fix this problem so I don't have to ruin my tunnels forever.