Relationship going toxic

I’ve been in a relationship with this guy for almost 5 months now. We started out as coworkers and he’s about 7 years older than me; I’m 22. He has since gotten a new job and I still am at the same work place. Pretty early on, he started making accusations saying how I was cheating on him and flirting with other coworkers and telling me to just go fuck someone else like the 22 year old that I am. I have never been one to party, drink, and definitely am not a cheater. These accusations blow my mind and drive me up the fucking wall. He’s said that I have slept with another coworker in the back of their car and even sent nudes to another one, neither of which are true. No matter what I say, how much time I spend with him, he still insists I’m a snake and I’m a liar. I want more than anything to make this work because I’ve experienced how beautiful it is when we’re in sync and on the same page. I don’t know what deep dark corner of his mind this shit comes from but it drives me NUTS. He has said “it’s unfortunate we couldn’t work out” and “good luck in the future” and every cliche break up line in the book. I’m literally going crazy like I genuinely haven’t done anything and I spend most of my time thinking about him. Today he literally made me lunch and we were making normal conversation over text earlier… now he wants to go to sleep and wish me well in life like he’s never gonna see me again. I know the simple solution is to let him go but I’m stubborn and I want him and I want this to work. Maybe I’m stupid. It’s causing my emotions to skyrocket and then rapidly decline and it’s making me feel physically unwell some days. Has anyone else ever experienced this?