I thought I'd chime in with my own perspective. I'm not a huge erotica reader, nor am I a huge erotica writer. I've only read a small number of erotica novels (though they have been almost entirely from AWers, so I guess I'm reading the good stuff?) and I've only attempted to write erotica once, culminating in a 40k novella.
But for me...
I don't see a real problem with using the word lover. It might be because I wrote a lesbian love story in 3rd person, so I welcomed the word openly. But I still used it once or twice in sex scenes - the sort of sex scenes that weren't focussed primarily on sex, but rather being with someone you love. I guess in that respect it went closer to steamy romance than to erotica... (Maybe... I'm a little iffy on definitions... don't sue me!)
But what I'm trying to say is - I don't see a problem with using the word "lover" when your 2 characters know they are in love (and FWIW, a conspicuous absence of that word, once you've set the precedent of using it liberally, though hopefully not excessively, IMO can help signal trouble in the relationship). Also, I don't see a problem with using it in sex scenes that are about love more than sex.
Take this with a grain of salt though. Like I said, I haven't read a whole lot of erotica, and I've only written about 7 sex scenes in my entire life... no, make that 8. 1 long one found its way into my recent Urban Fantasy.
