What would I do? If he is much younger than me that would mean he would be around 14 ....and I definitely see a problem with that haha .
Being serious now, I don't know why older guys tend to look for much younger ladies, but I have noticed that this is very common. Call me intolerant but I think it's a little creepy if a 30 something man is flirting with me since I barely reached the age of majority. I'm not saying that this is the case everywhere, but if you look to what happens outside in the world, not among christians, you notice that old guys get with young girls my age and it is usually because of lust .... just look at Hugh Hefner.
Is it possible that christians do the same for the same reason? I think you need to consider certain circumstances before judging, but I think it is very possible. Maybe the reason why younger guys are attracted to you is the same, I've heard that some men think it's sexy to date someone older than them (hey they said it! not me

) and not to mention that you do look younger, at least in the few pictures you have shared here .
I think the only thing you can do is being sure of their intentions, and wait...and pray, and wait, and pray again

. Obvious suggestion, but I really don't know what else you could do, maybe throw a party for 39 and older people only haha, but then you wouldn't know who is creepy and who is not....so yeah don't do that.