You are in a bad situation, and it is not your fault. You note that "Jeremy" is "really nice", but in fact, his actual behavior shows that he is not nice at all. He is acting predatory and inappropriately. He may or may not be self-aware enough to realize this, but "nice guy" is a mask covering this, no matter his internal justification.
I am around the same age as "Jeremy". I grew up in the 1980s when a typical movie plot might involve a "nice guy" who "just doesn't know how to talk to girls" doing something like this, and in the end he would "get the girl". Even then, we knew this was smarmy even if we excused it in fiction. Now, in 2019, there's really no excuse. However, Jeremy may still in his head be living in horrible 1980s rom-com, with a lot of "poor me, I am so nice but never get rewarded with the romantic attention other men get even though they are not nice like me" resentment in his head. I don't know what's in his head — that's a charitable reading. The other alternative is that he's a full-on wolf in sheep's clothing.
In either case, confronting him directly is not your job — and not likely to result in the best outcome for you. You should do one or more of:
- Talk to your company's human resources department.
- Talk to your boss.
- Talk to a lawyer with expertise in this area.
The third suggestion is not because you need to start a lawsuit, but because you need expert, professional help with the terrible situation this man has put you in. The other options may not get the results you really need. HR's job is to protect the company from liability, and hopefully their response will be supportive and decisive — but it may not. Your boss may react in a completely unhelpful way: you say he has been present when this has happened before, and he's done nothing. He may just be very unobservant, but he may also be complicit. So, talking to HR and your boss are the right steps, but you should be prepared for those actions to not be as helpful as they should be.
The minor good news in all of this, if we can call it that, is that we are at a moment culturally where these things are taken seriously and the tendency towards disbelief and victim-blaming at least reduced, although many of the answers and comments here show that it has not completely gone away. I wish I could promise that you'll be believed and trusted by authority figures (HR, the boss, the policy), but the fact is you may not. So, again, find a lawyer and and advocate. There may also be organizations in your area interested in supporting you. Look for those and get help!
In fact, you really need to be prepared to change employers entirely. I know that's more easily said than done (although, really, every employee of every company should have a contingency plan in mind in case something happens). But given the situation involved, it may ultimately be your only option. There are plenty of workplaces which would not put up with this. You deserve that. If you raise the issue and it turns out your current company does not have enough respect for you to make the situation right, you should go somewhere that does.