THIS IS THE TIME... Seperation anxiety is probably setting in. With my son it hit at 9 months, 8 with my daughter. I couldn't even go to the bathroom without screams echoing from the halls. I used to even leave the front door open wide while getting groceries out of the car and just crossing the threshold of the door would send my son screaming into thinking I was ABANDONING him!! LOL
My son had reflux for a little while, but was usually accompanied by vomiting or spitting up (when he was real little). I would go more in the seperation anxiety direction. All kids go through it. I would finally have the kids sleeping through the night, then it hit!! Also, when they get close to a year old, they also start to dream, as if you didn't have enough to worry about. They dream about things that happened durring the day, a commercial or anything, but inmature brains don't translate the images so well (as I've been told). Things can be really scary for a little child. Growing independence, exploring on their own, it's all kind of scary to them but exiting! AND NOW YOU WANT TO LEAVE THEM ALONE IN THE DARK?? He He. It's just night time, but since their new found imaginations are running wild... so will the scary things in their little lives. The dark is scary and mom leaving (walking out of the room) is also scary.
I was told once that it is a good time to play the peek-a-boo game (if you haven't already). Hide toys under blankets and ask them to find the toy, put the toy in a cupboard and ask them "where did it go?" "See, it's not gone, we just couldn't see it." Do the same with closets (you can hide yourself) and the bathroom too. This gets them used to the idea that you didn't abandon them, they just can't see you..... worked for me.
As for the seperation thing, they will grow out of it, promise, just takes a while.
Good luck, it's so hard to not worry with the first child anyway, but by the time the second comes, things just wont seem so hard or scary!