My husband has BPD, he told me about it before we even met face to face to give me a chance to see if it was something that I was willing to accept and give him a chance with.
I know that if he had kept it from me and ended up having an episode before telling me I doubt I would not have been able to let that go, and it would have destroyed him in that I was abandoning him at a time when he was vulnerable.
I also wouldn't have been able to look up strategies for when he feels negative about me and would likely have left when dating because what's the point in being with someone who seems to hate you? (luckily with him it happens rarely and I know that he will get over it in a few days so I just go about my business around him)
If you have a history of ending up in hospital or being arrested then that sounds pretty serious so I would definitely tell him now before something like that happens - for both you and him.
It sounds like you need to accept your diagnosis and seek counselling/ medication if you have not done so already - my husband is on medication and whilst he still deals with low moods etc regularly he hasn't had any serious episodes in many years.
We have been together for 6 years but only because he was honest when we were first chatting. Like a PP said, if you didn't know you were dating a sociopath then you wouldn't be happy about that when you found out - the main difference is that if a sociopath is rejected they likely wouldn't care whereas you very much would.