the finger in the mouth thing... it's a sensuality thing... a woman's mouth is a very sensual thing and guys like to see it in action,... on many different appendages if you get my drift...it also may make different men think about oral,.. seeing something go in and out of your mouth. that in and of itself can be arousing to them.
as for the hickie thing,... it can be a ownership thing... like marking their territory however odd that may sound,... or it could just be that they like your response so much to them sucking on those areas that they get carried away.
If your guy was to lick and suck on your fingers, one at a time, it would probably get you excited. Fingers do have nerve endings and when licked or sucked it can be a real turn on.
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