My iMessage texts haven't been sending since I've gone on vacation?

Ever since I went on vacation to another state, my texts have been messing up between me and my boyfriend.
My boyfriend has an iPhone 4, but he ran out of data so he can only use iMessage when he's on wifi and he messages me through his email.
I have an iPod Touch that I use to iMessage him when I'm on wifi, and I also have an old 'dumb phone' that I use to message him when I'm not on wifi, and I'll send him messages through his email address since he's out of data.
The past few days that I've been on vacation though, he hasn't been getting some of my messages through iMessage even though mine say 'delivered', and I haven't been getting some of his messages through my dumb phone. His wifi is really bad at his house, but this didn't start happening until I went on vacation and started using my friend's wifi.
What do you think the deal is? A phone issue? Wifi issue?

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