Ok the whole "forgetting to wear your underwear" comment before is bullsh*t. Your probably of legal age and can decide for yourself what you sexually want to do, but putting your professor in an unacomrotable situation by seeing your muff might be a major turn off for him. If you want him, do what you have to do, your a girl, so work those t*ts and @ss.... so yeah
dont do anything, your just a wee lass with a crush.
If he notices and starts sweating- then you know he wants you too.
If he askes you to stay after class-Well you can take it from there...