By Sally Fahey

If you think you’ve got relationship problems, check out how Sixers Benny Simmons, who was just crowned NBA rookie of the year, is spending his summer:

Beefing up security in L.A. because he says he’s being stalked by an ex.

According to TMZ Sports:

Benny believes his ex, Tinashe, has been tailing him and showing up at the same places he parties with Kendall Jenner… and it’s gotten so bad he’s seriously thinking of significantly beefing up security.

Sources close to Simmons tell TMZ Tinashe’s been suspiciously popping up regularly at places he goes with Kendall … way past the point of coincidence. You’ll remember, the singer showed up at Delilah Thursday, and a couple weeks prior she surfaced at Poppy in WeHo when Ben was there.

We’re told Ben is convinced Tinashe cannot accept the fact he ended their relationship and has moved on with Kendall. He believes she’s showing up to keep tabs on him so she can see if there’s a chink in the armor between him and Kendall.

Our sources say Ben thinks she’s become so obsessive he doesn’t want to take chances … especially because of Kendall, and that’s why he’s talking about hiring extra muscle.

Tinashe claimed Ben was texting her as she left Delilah Thursday night but, as we reported, she apologized to him the next day and acknowledged she lied.