This is weird. But I'm 20 years old, male, and a virgin. Lately in the past months I've been really turned on by girls more than usual and especially by older women around 35-50 of age. Why?

Normal. That's not weird, it's normal. Your hormones are active. Maybe you're attracted by an older woman and so older women that look like her are catching your eye. Go, meet, and talk to some women - either your own age or older. Even if it's not romantic, you may develop some friendships.