J Lo Solo in Portofino with Necklace Bearing Ben Affleck's Name

Jennifer Lopez is always in the presence of her BF, Ben Affleck, even if he's not physically there ... because he always hanging around ... her neck!

J Lo continues on her birthday vacay without Ben in Portofino, Italy. She strolled through the city Saturday ... wearing a necklace with Ben's name front and center.

We're told Ben is actually heading back to U.S. soil, so J Lo's hanging out on the yacht without him.

Now that Ben's gone, J Lo's been on her phone nonstop, texting and FaceTiming to occupy her time.

As for the bling ... it's a custom Foundrae charm necklace that Ben gave Jen for her 52nd birthday.

Seems a shame J Lo's now solo on the yacht ... it runs $1.1 million a week, and has all sorts of toys and amenities. In other words, it's awesome!

Before leaving for the U.S. ... Ben joined Jen at a restaurant in Italy, but food seemed secondary as they were all over each other as diners watched.