Op you poor thing, I know just how upsetting it can be, it has happened to me twice.
First started at secondary school, there was a boy I knew and we'd been to primary school together, we were never particularly close, but he was always on the edge of a group I hung out with.
In the last two years of secondary school, he asked me out a few times, I'd said no but he carried on trying to ingratiate himself with me, would turn up at places I went with friends etc.
One day near the end of school, he was waiting at the school gates and said he'd walk me home, I brushed him off but he basically tailed me the whole way home, I began to feel quite afraid and a few times turned around and told him to go away etc. He followed me up the stairs in my building and tried to sexually assault me. I got free but was left very shaken. Stupidly I never reported it or told my parents, just avoided him as much as possible from there on out. He actually tried to add my on FB when I joined it but I blocked him.
The second was when I was alost 18 and at college, I worked part time in a supermarket on the checkout. One day a letter and a bunch of flowers were ledt at customer services with my name on. I hadn't a clue who theyr were from but the letter was full of poetry and declarations of love etc. I thought it was a joke to be honest. Then gifts for me kept being left there, still had no clue who from.
One day at work a customer came along who was buying champagne, a jar of caviar, chocolates, scented candles etc I finished scannign it all and the man who paid told me it was all for me and he was taking me out on a date that night and what tiem should he pick me up. I was horrified, he was old enough to be my Dad, was leering at me over the till and I was in complete shock. I caught my supervisors attention who realised I was in distress and was whisked off to the staff room on the pretense I was ill.
He came into the supermarket every single day afterwards, and paced up and down the checkouts lookign for me, if he saw me he'd approach and try to convince me we were destined to be together etc. He had to be abnned from the store, then began waiting at the bus stop outside waiting for me. My Dad had to start pickign me up and we had to call the police to warn him off.
It was terrifyign and I have every symapthy for you OP, please do not let this man intimidate or frighten you, confide in a trusted friend and either get someone to call him out over his behaviour in front of your group (shaming him?) or involve the police if you feel afraid.