I kind of think that excessive gas is made due to anxiety. I don't know if you are a particularly anxious person, or if you are in the midst of stressful events to make your system busier than usual.

It made me smile to think that your family only passes gas in the bathroom. I've often heard that's the only place you should do such, but sometimes, it doesn't wait!

My feeling is, if you are comfortable enough to have him spend the night with you, it's probably important, at least for your own peace of mind, to discuss this with him before the time arrives. Just be honest, and keep it light and funny, yet serious, too. Laugh about it with him, but let him know that this is embarrassing to you, but it happens. See how he responds. If he's a good guy, he will understand.

Hope this goes well for you, and hope you'll come back and post again to let us know what happened, what worked, and what didn't.