Robin Thicke -- Who's Been Sleeping in My Bed? A Young, Hot Model!

Robin Thicke is banging a hot model who's either 19 or 20 ... and the reason we know is that she took pics of herself in a bed ... that we found out belongs to Robin!

April Love Geary has been seen with Robin over the last few months. The model -- who said in a June interview she was 19 -- has posted photos over the past few months of rooms that match up perfectly with Robin's house.

We got pics of Robin's house from the real estate company that listed Robin and Paula Patton's home after she filed for divorce.

April posted a selfie on October 2 of her laying in bed, drinking coffee. The headboard and photo above the bed are an exact match to the ones in Thicke's bedroom.

A few weeks later, she posted a sweet shot of a bunch of roses with the caption "Look what I got." The table, the chairs, the mirror ... match, match, match.

Then on November 1, April posted another selfie ... with matches all over the place from his bathroom.

If you still have doubts, Thicke bought her this skimpy costume during a Halloween hottie shopping spree.