"The Flea"

I believe this poem is about sex, which does not surprise me any more.  The guy in the poem says that they both have been bitten by the flea, so both of their blood is messed up, so if they have sex, it won't matter.  In the first stanza, the guy is trying to get her to sleep with him, and in the second stanza, it is pretty much him trying to get her to sleep with him again.  The third stanza has the flea dying and and nothing is wrong with their blood so they won't get weaker if they sleep together.