Guy wants sex more during fertile window?

So I've notice since starting glow that my boyfriend, who doesn't have a very high sex drive, always wants to have sex during my fertile window! Usually I have to initiate the sex and we have it about once a week. But during my fertile window he wants it everyday for about 4 or 5 days than is back to normal. He isn't on glow so he doesn't know my fertile days or anything. I'm not complaining by any means it's wonderful actually but it's just strange to me. Does this happen with anyone else's guy?