Almost stalking??

Me and my so split up for 6 months a while back and I started seeing somebody else for a only a couple of weeks because he was a bit of a d*ck, well anyway me and my so got back together and now have a really good relationship things have never been so good between us, and now the person I was seeing for a couple of weeks has been pretty much stalking me telling me he loves me wants to be with me constantly texting around 15 times a day and to not block him because it will just get him pissed more and saying he's going to speak to my so and tell him we've been having sex (even though we haven't) just to break us up, he's found out where I live, he's waited for me outside of my work a few times just to threaten me and I get texts off of him saying his guy friends have seen me flirting and looking at other guys and how much of a whore and slut I am. I just don't know what to do anymore I don't want to tell my so just in case there is the possibility he might believe him 😭 I just want some advice on what to do we are in our 30s and I feel like a helpless child right now I'm sick of living in fear