Disclosure can be a slippery little sucker - you think you know what you're going to say, how you'll say it, how you'll cope...next thing you know they react differently to what you expected (they don't cope - Help! or they DO cope - double Help!!), then you're back-pedalling or over-sharing and GAH, WHY did I do this!?!
There's sharing and sharing. Different relationships need different approaches. If you're friends are depressed, their capacity to actually hear what you're saying could be in doubt. With your boyf - you'd want some kind of heads up if it was him, yeah?
There can be a lot of emotions come out of the woodwork unexpectedly when you disclose ("OMG, the shame, I can never face them again), so I'd err on the side of caution.
I have an anniversary on 3 January and I know, every year, it's gonna send me into a tailspin. But the people that are close to me (the ones where it's helpful if they know to take it easy with me) already know I've got PTSD, so I just tell them "3 January is an anniversary for me and it's usually pretty nasty, so if I don't return your call, sorry in advance, hey".
Haven't really told them didley squat. They're gonna learn soon enough that I'm a mole to be around that day, and it just gives them context. No big deal.
If you decide to share more, specially with your boyf, be clear in your mind what you want to share and why. What do you want him to do with the info - maybe it's to share and build intimacy, maybe it's so he keeps his mother out of your warpath. Don't just dump the info, tell him why you're telling him.
Finally, be ready for questions, and ready to draw boundaries. If you share info with them, they're free to ask questions, and you're free NOT to answer them. Know where you share-limit is, and be confident in saying "look, I'm really grateful for your concern, it's really reassuring...but I'm just not ready to talk about it in more detail right now".
It can be super helpful to have support people who know and understand. But you need to be comfortable, they need to be ready, and while the odds are you'll get a whole big serving of compassion if you share, you can't actually control their response.
People here have lots of different disclosure experiences. Measure up your own position against the different opinions.
Best wishes over your anniversary - the clock keeps ticking, the day will pass:)