Why do I wake up with bruises or bite marks?

I swear something bites me at night and I don't know what! I am kinda of worried! First it was my leg and now my neck and I dunno! I don't think its normal! It looks like mosquite bites but they aren't they are more round! What you think! I am so serious... I hope its not something bad!
Why do I wake up with bruises or bite marks?
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