Generally, farting is a result of two things: Diet and gastric bateriae.
If you find yourself suddenly farting more, and your diet hasn't changed, it could be some kind of stomach germ. You might have eaten food that had started to go bad, or which contained certain bacteriae to begin with. If microbiota is the problem, it'll very likely stop on its own.
There's some chance that you're simply noticing the fact that you're passing gas more than you would normally, since it doesn't feel embarassing whilst you're alone.
In any case, it's highly probable that your boyfriend will get used to it - after all, he did with himself. If you happen to do it, I suggest apologetic humour - Make a fake embarassed face and say "oops" or something.
It's also possible to regulate the passing of gas based on when you eat. If you're full, you're much more likely to fart. My diet involves fasting every other day, which means I only really pass gass on the days I eat. Depending on your physiology, it might be a sensible choice to not eat in the hours before seeing your partner.
But I really do think the best choice is to just get used to it and try not to think too much about it. Your boyfriend would be extremely foolish if he turned it into an issue.
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